From mboxrd@z Thu Jan 1 00:00:00 1970 Received: by ug-out-1314.google.com with SMTP id s2so1522921uge for ; Wed, 29 Nov 2006 01:27:54 -0800 (PST) Message-ID: <6d6a94c50611290127u2b26976en1100217a69d651c0@mail.gmail.com> Date: Wed, 29 Nov 2006 17:27:52 +0800 From: Aubrey Subject: Re: The VFS cache is not freed when there is not enough free memory to allocate In-Reply-To: <4e5ebad50611282317r55c22228qa5333306ccfff28e@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <6d6a94c50611212351if1701ecx7b89b3fe79371554@mail.gmail.com> <1164185036.5968.179.camel@twins> <6d6a94c50611220202t1d076b4cye70dcdcc19f56e55@mail.gmail.com> <456A964D.2050004@yahoo.com.au> <4e5ebad50611282317r55c22228qa5333306ccfff28e@mail.gmail.com> Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: Sonic Zhang , Peter Zijlstra , linux-kernel@vger.kernel.org, linux-mm@kvack.org, vapier.adi@gmail.com List-ID: On 11/29/06, Sonic Zhang wrote: > Forward to the mailing list. > > > On 11/27/06, Nick Piggin wrote: > > > >> I haven't actually written any nommu userspace code, but it is obvious > >> that you must try to keep malloc to <= PAGE_SIZE (although order 2 and > >> even 3 allocations seem to be reasonable, from process context)... Then > >> you would use something a bit more advanced than a linear array to store > >> data (a pagetable-like radix tree would be a nice, easy idea). > >> > > > > But, even we split the 8M memory into 2048 x 4k blocks, we still face > > this failure. The key problem is that available memory is small than > > 2048 x 4k, while there are still a lot of VFS cache. The VFS cache can > > be freed, but kernel allocation function ignores it. See the new test > > application. > > > Which kernel allocation function? If you can provide more details I'd > like to get to the bottom of this. I posted it here, I think you missed it. So forwarded it to you. > > Because the anonymous memory allocation in mm/nommu.c is all allocated > with GFP_KERNEL from process context, and in that case, the allocator > should not fail but call into page reclaim which in turn will free VFS > caches. > > > > > What's a better way to free the VFS cache in memory allocator? > > > It should be freeing it for you, so I'm not quite sure what is going > on. Can you send over the kernel messages you see when the allocation > fails? I don't think so. The kernel doesn't attempt to free it. The log is included in the mail I forwarded to you. > > Also, do you happen to know of a reasonable toolchain + emulator setup > that I could test the nommu kernel with? A project named skyeye. http://www.skyeye.org/index.shtml -Aubrey -- 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