From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f69.google.com (mail-pa0-f69.google.com [209.85.220.69]) by kanga.kvack.org (Postfix) with ESMTP id 2D3836B007E for ; Fri, 13 May 2016 02:22:33 -0400 (EDT) Received: by mail-pa0-f69.google.com with SMTP id yl2so136285456pac.2 for ; Thu, 12 May 2016 23:22:33 -0700 (PDT) Received: from lgeamrelo12.lge.com (LGEAMRELO12.lge.com. [156.147.23.52]) by mx.google.com with ESMTP id e11si22572846pfb.36.2016.05.12.23.22.31 for ; Thu, 12 May 2016 23:22:32 -0700 (PDT) Date: Fri, 13 May 2016 15:23:03 +0900 From: Minchan Kim Subject: Re: [PATCH] zram: introduce per-device debug_stat sysfs node Message-ID: <20160513062303.GA21204@bbox> References: <20160511134553.12655-1-sergey.senozhatsky@gmail.com> <20160512234143.GA27204@bbox> <20160513010929.GA615@swordfish> MIME-Version: 1.0 In-Reply-To: <20160513010929.GA615@swordfish> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline Sender: owner-linux-mm@kvack.org List-ID: To: Sergey Senozhatsky Cc: Sergey Senozhatsky , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org On Fri, May 13, 2016 at 10:09:29AM +0900, Sergey Senozhatsky wrote: > Hello Minchan, > > On (05/13/16 08:41), Minchan Kim wrote: > [..] > > will fix and update, thanks! > > > > > @@ -719,6 +737,8 @@ compress_again: > > > zcomp_strm_release(zram->comp, zstrm); > > > zstrm = NULL; > > > > > > + atomic64_inc(&zram->stats.num_recompress); > > > + > > > > It should be below "goto compress_again". > > I moved it out of goto intentionally. this second zs_malloc() > > handle = zs_malloc(meta->mem_pool, clen, > GFP_NOIO | __GFP_HIGHMEM | > __GFP_MOVABLE); > > can take some time to complete, which will slow down zram for a bit, > and _theoretically_ this second zs_malloc() still can fail. yes, we > would do the error print out pr_err("Error allocating memory ... ") > and inc the `failed_writes' in zram_bvec_rw(), but zram_bvec_write() > has several more error return paths that can inc the `failed_writes'. > so by just looking at the stats we won't be able to tell that we had > failed fast path allocation combined with failed slow path allocation > (IOW, `goto recompress' never happened). > > so I'm thinking about changing its name to num_failed_fast_compress > or num_failed_fast_write, or something similar and thus count the number > of times we fell to "!handle" branch, not the number of goto-s. > what do you think? or do you want it to be num_recompress specifically? Sorry, I don't get your point. What's the problem with below? goto compress_again so atomic_inc(num_recompress) My concern isn't a performance or something but just want to be more readable and not error-prone which can increase num_compress although second zs_malloc could be failed. When I tested with heavy workload, I saw second zs_malloc can be fail but not frequently so it's not theoretical issue. What's the your concern with below? Sorry if I don't get your point. Please elaborate it more. diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index a629bd8d452b..8bdcc4b2b9b8 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -737,12 +737,12 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index, zcomp_strm_release(zram->comp, zstrm); zstrm = NULL; - atomic64_inc(&zram->stats.num_recompress); - handle = zs_malloc(meta->mem_pool, clen, GFP_NOIO | __GFP_HIGHMEM); - if (handle) + if (handle) { + atomic64_inc(&zram->stats.num_recompress); goto compress_again; + } pr_err("Error allocating memory for compressed page: %u, size=%zu\n", index, clen); -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org