From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexey Starikovskiy Subject: Re: [patch][rfc] acpi: do not use kmem caches Date: Mon, 01 Dec 2008 20:32:41 +0300 Message-ID: <49341FB9.80702@gmail.com> References: <20081201083128.GB2529@wotan.suse.de> <84144f020812010318v205579ean57edecf7992ec7ef@mail.gmail.com> <20081201120002.GB10790@wotan.suse.de> <4933E2C3.4020400@gmail.com> <20081201133646.GC10790@wotan.suse.de> <4933F14C.7020200@gmail.com> <20081201171806.GA14074@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from ey-out-2122.google.com ([74.125.78.27]:25265 "EHLO ey-out-2122.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752106AbYLARcr (ORCPT ); Mon, 1 Dec 2008 12:32:47 -0500 Received: by ey-out-2122.google.com with SMTP id 6so1091037eyi.37 for ; Mon, 01 Dec 2008 09:32:45 -0800 (PST) In-Reply-To: <20081201171806.GA14074@infradead.org> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Christoph Hellwig Cc: Nick Piggin , Pekka Enberg , Linux Memory Management List , linux-acpi@vger.kernel.org, lenb@kernel.org Christoph Hellwig wrote: > On Mon, Dec 01, 2008 at 05:14:36PM +0300, Alexey Starikovskiy wrote: > >> Why then you try to delete ACPICA code, which might be just disabled by >> undefining ACPI_USE_LOCAL_CACHE? >> If you do want to go that path, you need to create patch against ACPICA, not >> Linux code. >> > > Sorry dude, but that's not how Linux development works. Please talk to > some intel OTC folks to get an advice on how it does. > > We are not speaking about Linux code here -- Nick changed ACPICA files. And he already admits, that his patch is at least half-way wrong. Sorry dude, ACPICA code is not Linux only, so one needs some care while dropping some functionality from it. >>> Ah OK I misread, that's the cache's freelist... ACPI shouldn't be poking >>> this button inside the slab allocator anyway, honestly. What is it >>> for? >>> >>> >> And it is not actually used -- you cannot unload ACPI interpreter, and >> this function is called only from there. >> > > Care to remove all this dead code? > > It is used at least in Windows userspace programs. So, removing these 4 lines only from Linux will create another headache for Len during his merging of each new ACPICA release into Linux. >>> Is there a reasonable performance or memory win by using kmem cache? If >>> not, then they should not be used >>> >> ACPI is still working in machines with several megabytes of RAM and >> 100mhz Pentium processors. Do you say we should just not consider them >> any longer? >> If so, then just delete all ACPICA caches altogether. >> > > As Nick is trying to explain you for a while it's not actually going > to be a performance benefit for these, quite contrary because of how > slab caches waste a lot of memory when only used very lightly or not > at all. > > If you care to do the math, and I helped you in another posting, he may save about 11k in 32bit mode on thinkpad, and loose 70k in 64bit mode on similar thinkpad. Regards, Alex.