From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 264CEC433FE for ; Thu, 17 Nov 2022 00:24:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:From:References:Cc:To: Subject:MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=kXuKIpSQmaA7aAPou3bmWv48rD2yQth9V9KPdxSeosA=; b=NDKlYM9QSRVFZ/ 6q7B/IDtuAa2YJ9/45FiO0q5qAWJADCalr2+SIf9YMDvAW+bRhqI72Eznub2gu2oWSckAYR/AvCCn Sss8ZEMh68+fXawMVwP8c8fMNJI0UFRADJmnaDfu4wCrVsxWlXdy/9TK6G0afgA+W7YnGbFI5bR3C CZQl9KKdYlT/eQMsgZyw3EX3lHwR/WVhPz8znRUxrcTmF+keTm7jG4lTxNrLpsHQ1NcCbOhYvblEq yHxBjaMBv7/76ctGQnaBhvSCx7kC6gUGu7rc3R3DIsnyQqVBTWFgRHofD+C008rJQy2CJZlX+S3A/ pdG/+BkdXRUJec+EgnTA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1ovSgF-008xsy-K9; Thu, 17 Nov 2022 00:22:59 +0000 Received: from esa3.hgst.iphmx.com ([216.71.153.141]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1ovSgA-008xic-3d for linux-arm-kernel@lists.infradead.org; Thu, 17 Nov 2022 00:22:56 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=wdc.com; i=@wdc.com; q=dns/txt; s=dkim.wdc.com; t=1668644573; x=1700180573; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=KXoWRv8rOB1+AtNCLdxcm0lfGHxErPjhaM0+VnSkGxw=; b=X9AcsnOCA4sqewVOWXXMuUr4Mq1Y+nRyFMSGpA025wFF5o4PoRrcq8wv 9q78DxNo+IrE5zyu+avsqniaiEjeQ4C8x3qZOrbBfAQDfewbh9VewiPtE wEI9mbJcEfwXYt4QlRbUHzPJ6/hRqt1xYheHJbnJSUTMeraAWZdGfBL64 WJou+J58KqC8LpSaGBWovpRJofsBOrdR4TdqyboEZckOQH4YHo+EQpCzj ylYknVMuWz1UN8ExdEftAp1WlgymC4g2PR0cJDaITnwuKk01iYUPA1o2a zeg61TBymUs4aqyYU4QJrfF3RFh5sAgzivcssBua5PJFVmMcYtPRA+ESZ Q==; X-IronPort-AV: E=Sophos;i="5.96,169,1665417600"; d="scan'208";a="221621139" Received: from uls-op-cesaip02.wdc.com (HELO uls-op-cesaep02.wdc.com) ([199.255.45.15]) by ob1.hgst.iphmx.com with ESMTP; 17 Nov 2022 08:22:49 +0800 IronPort-SDR: D4Ev+HsHMt/MbL/zlPF+809SxbLXoAXOsDs2RFgCxLYMTACX0bayVksKbtYiAaAHiw9zSRq6k1 Ws/JrzjsCkuyiIniaF1uHQmTRXRPFHEWtwqelVHkjevfPlgjb0zhsn+x3+/cxEDqv8bMJQi4wT 8D8mIFg6Aw+FwsqXOQ1uVUTnEJJw/XpL9gfed1a15FA6EyRsB/uOlVmHv5Fa8GCr1htS864cXw iIWDBZcHjreOENQMbSr+AWRzrZ2TqPhp+sUAs87wmcQptMQahkm/kjLkdA6jE2+C5hI5VxiSe3 ijc= Received: from uls-op-cesaip01.wdc.com ([10.248.3.36]) by uls-op-cesaep02.wdc.com with ESMTP/TLS/ECDHE-RSA-AES128-GCM-SHA256; 16 Nov 2022 15:36:00 -0800 IronPort-SDR: xdlQ4mTLmMmVRLMMD2YxToL779LI3Zp3GArM50aHEUgUyYgFlzGGx22r2Nl5DhFY3NAirAmdU9 Y+86l737/OORaefM8HM/baCEZ1gR56RPMHIbRzVmP6TwPThF8qzZHabLDClkIxSnW36lU+0MfT N+dnbAh5R/3SAnRFpsZoyKrtXdm/wZ6qESiPBFQvGAq6dZj6qYAEqWCUPvkT8oRo9DBVIjZYCg Qd4T81K7VDyGTsrt3VteR52NZl7HLWTE2G0rZryANcU4Hfo7b+NfM8d57Kwdgr2BY0kNbNuFeD a5c= WDCIronportException: Internal Received: from usg-ed-osssrv.wdc.com ([10.3.10.180]) by uls-op-cesaip01.wdc.com with ESMTP/TLS/ECDHE-RSA-AES128-GCM-SHA256; 16 Nov 2022 16:22:50 -0800 Received: from usg-ed-osssrv.wdc.com (usg-ed-osssrv.wdc.com [127.0.0.1]) by usg-ed-osssrv.wdc.com (Postfix) with ESMTP id 4NCLGc1Zymz1RWxq for ; Wed, 16 Nov 2022 16:22:48 -0800 (PST) Authentication-Results: usg-ed-osssrv.wdc.com (amavisd-new); dkim=pass reason="pass (just generated, assumed good)" header.d=opensource.wdc.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d= opensource.wdc.com; h=content-transfer-encoding:content-type :in-reply-to:organization:from:content-language:references:to :subject:user-agent:mime-version:date:message-id; s=dkim; t= 1668644565; x=1671236566; bh=KXoWRv8rOB1+AtNCLdxcm0lfGHxErPjhaM0 +VnSkGxw=; b=gRMWbOlPsdLeCiiHC3i3Yik1iPT7sbuSiGhiWShHj9gmBY3LFXJ 3lde1xjqjzx5uLR4A4sNUq8fanQ9skU2D/Lxs+40sAkSe6CgjcPXCDSjGcWstjZQ vRMm0kE72PqfwWIPIKdjVoI82UhN4VlJj5mXzCa1rN/Etb49y0Nk8Doj7T2Xe/W/ blIp5c2gGkY22HeS6wDwrv7IUa/baKIkHgWYxmj/XpLzQ7HQkhDuLQ5fXiCHycc5 cxnT4d1EpQev4GuDuazQVayHtlAVmzWnDkVse4mXqyceaE1F6kA4A/aHkdRv48DI hqxTXJXq/zfz3BGb1MRUI1dQv8n5/aPTcRw== X-Virus-Scanned: amavisd-new at usg-ed-osssrv.wdc.com Received: from usg-ed-osssrv.wdc.com ([127.0.0.1]) by usg-ed-osssrv.wdc.com (usg-ed-osssrv.wdc.com [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id r0a0diHGO0eI for ; Wed, 16 Nov 2022 16:22:45 -0800 (PST) Received: from [10.225.54.48] (unknown [10.225.54.48]) by usg-ed-osssrv.wdc.com (Postfix) with ESMTPSA id 4NCLGS0lckz1RvLy; Wed, 16 Nov 2022 16:22:39 -0800 (PST) Message-ID: Date: Thu, 17 Nov 2022 09:22:38 +0900 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.4.2 Subject: Re: Deprecating and removing SLOB To: Vlastimil Babka , Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: Conor Dooley , Pasha Tatashin , Christoph Lameter , David Rientjes , Joonsoo Kim , Pekka Enberg , Matthew Wilcox , Roman Gushchin , Linus Torvalds , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Catalin Marinas , Rustam Kovhaev , Andrew Morton , Josh Triplett , Arnd Bergmann , Russell King , Alexander Shiyan , Aaro Koskinen , Janusz Krzysztofik , Tony Lindgren , Yoshinori Sato , Rich Felker , Jonas Bonn , Stefan Kristiansson , Stafford Horne , "linux-arm-kernel@lists.infradead.org" , openrisc@lists.librecores.org, linux-riscv@lists.infradead.org, linux-sh@vger.kernel.org, Geert Uytterhoeven , Conor.Dooley@microchip.com, Paul Cercueil References: <93079aba-362e-5d1e-e9b4-dfe3a84da750@opensource.wdc.com> <44da078c-b630-a249-bf50-67df83cd8347@suse.cz> <35650fd4-3152-56db-7c27-b9997e31cfc7@opensource.wdc.com> <97c0735c-3127-83d5-30ff-8e57c6634f6e@opensource.wdc.com> <452c3833-9275-37c7-3d48-5c996c0e2557@suse.cz> Content-Language: en-US From: Damien Le Moal Organization: Western Digital Research In-Reply-To: <452c3833-9275-37c7-3d48-5c996c0e2557@suse.cz> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221116_162254_176882_CED74D3A X-CRM114-Status: GOOD ( 46.58 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2022/11/17 2:51, Vlastimil Babka wrote: > On 11/15/22 05:24, Damien Le Moal wrote: >> On 11/14/22 23:47, Hyeonggon Yoo wrote: >>> On Mon, Nov 14, 2022 at 08:35:31PM +0900, Damien Le Moal wrote: >>>> On 11/14/22 18:36, Vlastimil Babka wrote: >>>>> On 11/14/22 06:48, Damien Le Moal wrote: >>>>>> On 11/14/22 10:55, Damien Le Moal wrote: >>>>>>> On 11/12/22 05:46, Conor Dooley wrote: >>>>>>>> On Fri, Nov 11, 2022 at 11:33:30AM +0100, Vlastimil Babka wrote: >>>>>>>>> On 11/8/22 22:44, Pasha Tatashin wrote: >>>>>>>>>> On Tue, Nov 8, 2022 at 10:55 AM Vlastimil Babka wrote: >>>>>>>>>>> >>>>>>>>>>> Hi, >>>>>>>>>>> >>>>>>>>>>> as we all know, we currently have three slab allocators. As we discussed >>>>>>>>>>> at LPC [1], it is my hope that one of these allocators has a future, and >>>>>>>>>>> two of them do not. >>>>>>>>>>> >>>>>>>>>>> The unsurprising reasons include code maintenance burden, other features >>>>>>>>>>> compatible with only a subset of allocators (or more effort spent on the >>>>>>>>>>> features), blocking API improvements (more on that below), and my >>>>>>>>>>> inability to pronounce SLAB and SLUB in a properly distinguishable way, >>>>>>>>>>> without resorting to spelling out the letters. >>>>>>>>>>> >>>>>>>>>>> I think (but may be proven wrong) that SLOB is the easier target of the >>>>>>>>>>> two to be removed, so I'd like to focus on it first. >>>>>>>>>>> >>>>>>>>>>> I believe SLOB can be removed because: >>>>>>>>>>> >>>>>>>>>>> - AFAIK nobody really uses it? It strives for minimal memory footprint >>>>>>>>>>> by putting all objects together, which has its CPU performance costs >>>>>>>>>>> (locking, lack of percpu caching, searching for free space...). I'm not >>>>>>>>>>> aware of any "tiny linux" deployment that opts for this. For example, >>>>>>>>>>> OpenWRT seems to use SLUB and the devices these days have e.g. 128MB >>>>>>>>>>> RAM, not up to 16 MB anymore. I've heard anecdotes that the performance >>>>>>>>>>> SLOB impact is too much for those who tried. Googling for >>>>>>>>>>> "CONFIG_SLOB=y" yielded nothing useful. >>>>>>>>>> >>>>>>>>>> I am all for removing SLOB. >>>>>>>>>> >>>>>>>>>> There are some devices with configs where SLOB is enabled by default. >>>>>>>>>> Perhaps, the owners/maintainers of those devices/configs should be >>>>>>>>>> included into this thread: >>>>>>>>>> >>>>>>>>>> tatashin@soleen:~/x/linux$ git grep SLOB=y >>>>>>>> >>>>>>>>>> arch/riscv/configs/nommu_k210_defconfig:CONFIG_SLOB=y >>>>>>>>>> arch/riscv/configs/nommu_k210_sdcard_defconfig:CONFIG_SLOB=y >>>>>>>>>> arch/riscv/configs/nommu_virt_defconfig:CONFIG_SLOB=y >>>>>>>> >>>>>>>>> >>>>>>>>> Turns out that since SLOB depends on EXPERT, many of those lack it so >>>>>>>>> running make defconfig ends up with SLUB anyway, unless I miss something. >>>>>>>>> Only a subset has both SLOB and EXPERT: >>>>>>>>> >>>>>>>>>> git grep CONFIG_EXPERT `git grep -l "CONFIG_SLOB=y"` >>>>>>>> >>>>>>>>> arch/riscv/configs/nommu_virt_defconfig:CONFIG_EXPERT=y >>>>>>>> >>>>>>>> I suppose there's not really a concern with the virt defconfig, but I >>>>>>>> did check the output of `make nommu_k210_defconfig" and despite not >>>>>>>> having expert it seems to end up CONFIG_SLOB=y in the generated .config. >>>>>>>> >>>>>>>> I do have a board with a k210 so I checked with s/SLOB/SLUB and it still >>>>>>>> boots etc, but I have no workloads or w/e to run on it. >>>>>>> >>>>>>> I sent a patch to change the k210 defconfig to using SLUB. However... >>>>> >>>>> Thanks! >>>>> >>>>>>> The current default config using SLOB gives about 630 free memory pages >>>>>>> after boot (cat /proc/vmstat). Switching to SLUB, this is down to about >>>>>>> 400 free memory pages (CONFIG_SLUB_CPU_PARTIAL is off). >>>>> >>>>> Thanks for the testing! How much RAM does the system have btw? I found 8MB >>>>> somewhere, is that correct? >>>> >>>> Yep, 8MB, that's it. >>>> >>>>> So 230 pages that's a ~920 kB difference. Last time we saw less dramatic >>>>> difference [1]. But that was looking at Slab pages, not free pages. The >>>>> extra overhead could be also in percpu allocations, code etc. >>>>> >>>>>>> This is with a buildroot kernel 5.19 build including a shell and sd-card >>>>>>> boot. With SLUB, I get clean boots and a shell prompt as expected. But I >>>>>>> definitely see more errors with shell commands failing due to allocation >>>>>>> failures for the shell process fork. So as far as the K210 is concerned, >>>>>>> switching to SLUB is not ideal. >>>>>>> >>>>>>> I would not want to hold on kernel mm improvements because of this toy >>>>>>> k210 though, so I am not going to prevent SLOB deprecation. I just wish >>>>>>> SLUB itself used less memory :) >>>>>> >>>>>> Did further tests with kernel 6.0.1: >>>>>> * SLOB: 630 free pages after boot, shell working (occasional shell fork >>>>>> failure happen though) >>>>>> * SLAB: getting memory allocation for order 7 failures on boot already >>>>>> (init process). Shell barely working (high frequency of shell command fork >>>>>> failures) >>>> >>>> I forgot to add here that the system was down to about 500 free pages >>>> after boot (again from the shell with "cat /proc/vmstat"). >>>> >>>>>> * SLUB: getting memory allocation for order 7 failures on boot. I do get a >>>>>> shell prompt but cannot run any shell command that involves forking a new >>>>>> process. >>>> >>>> For both slab and slub, I had cpu partial off, debug off and slab merge >>>> on, as I suspected that would lead to less memory overhead. >>>> I suspected memory fragmentation may be an issue but doing >>>> >>>> echo 3 > /proc/sys/vm/drop_caches >>>> >>>> before trying a shell command did not help much at all (it usually does on >>>> that board with SLOB). Note that this is all with buildroot, so this echo >>>> & redirect always works as it does not cause a shell fork. >>>> >>>>>> >>>>>> So if we want to keep the k210 support functional with a shell, we need >>>>>> slob. If we reduce that board support to only one application started as >>>>>> the init process, then I guess anything is OK. >>>>> >>>>> In [1] it was possible to save some more memory with more tuning. Some of >>>>> that required boot parameters and other code changes. In another reply [2] I >>>>> considered adding something like SLUB_TINY to take care of all that, so >>>>> looks like it would make sense to proceed with that. >>>> >>>> If you want me to test something, let me know. >>> >>> Would you try this please? >>> >>> diff --git a/mm/slub.c b/mm/slub.c >>> index a24b71041b26..1c36c4b9aaa0 100644 >>> --- a/mm/slub.c >>> +++ b/mm/slub.c >>> @@ -4367,9 +4367,7 @@ static int kmem_cache_open(struct kmem_cache *s, slab_flags_t flags) >>> * The larger the object size is, the more slabs we want on the partial >>> * list to avoid pounding the page allocator excessively. >>> */ >>> - s->min_partial = min_t(unsigned long, MAX_PARTIAL, ilog2(s->size) / 2); >>> - s->min_partial = max_t(unsigned long, MIN_PARTIAL, s->min_partial); >>> - >>> + s->min_partial = 0; >>> set_cpu_partial(s); >>> >>> #ifdef CONFIG_NUMA >>> >>> >>> and booting with and without boot parameter slub_max_order=0? >> >> Test notes: I used Linus 6.1-rc5 as the base. That is the only thing I >> changed in buildroot default config for the sipeed maix bit card, booting >> with SD card. The test is: booting and run "cat /proc/vmstat" and register >> the nr_free_pages value. I repeated the boot + cat 3 to 4 times for each case. >> >> Here are the results: >> >> 6.1-rc5, SLOB: >> - 623 free pages >> - 629 free pages >> - 629 free pages >> 6.1-rc5, SLUB: >> - 448 free pages >> - 448 free pages >> - 429 free pages >> 6.1-rc5, SLUB + slub_max_order=0: >> - Init error, shell prompt but no shell command working >> - Init error, no shell prompt >> - 508 free pages >> - Init error, shell prompt but no shell command working >> 6.1-rc5, SLUB + patch: >> - Init error, shell prompt but no shell command working >> - 433 free pages >> - 448 free pages >> - 423 free pages >> 6.1-rc5, SLUB + slub_max_order=0 + patch: >> - Init error, no shell prompt >> - Init error, shell prompt, 499 free pages >> - Init error, shell prompt but no shell command working >> - Init error, no shell prompt >> >> No changes for SLOB results, expected. >> >> For default SLUB, I did get all clean boots this time and could run the >> cat command. But I do see shell fork failures if I keep running commands. >> >> For SLUB + slub_max_order=0, I only got one clean boot with 508 free >> pages. Remaining runs failed to give a shell prompt or allow running cat >> command. For the clean boot, I do see higher number of free pages. >> >> SLUB with the patch was nearly identical to SLUB without the patch. >> >> And SLUB+patch+slub_max_order=0 gave again a lot of errors/bad boot. I >> could run the cat command only once, giving 499 free pages, so better than >> regular SLUB. But it seems that the memory is more fragmented as >> allocations fail more often. >> >> Hope this helps. Let me know if you want to test something else. > > Could you please try this branch with CONFIG_SLUB_TINY=y? > https://git.kernel.org/pub/scm/linux/kernel/git/vbabka/linux.git/log/?h=slub-tiny-v1r0 > > Seeing your results I didn't modify default slub_max_order by this new > CONFIG (yet?) so maybe after trying the default, trying then also with > manual slub_max_order=0 and slub_max_order=1 would be useful too. Otherwise > it should be all changes to lower SLUB memory footprint. Hopefully it will > be visible in the number of free pages. But if fragmentation is an issue, it > might not be enough. BTW, during boot there should be a line "Built X > zonelists, mobility grouping ..." can you grep for it and provide please, I > wonder if mobility grouping ends up being off or on on that system. OK. Will try as soon as I can (before end of week hopefully). My pipeline is a little crowded right now :) > > Thanks! > >> Cheers. >> > -- Damien Le Moal Western Digital Research _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel