From: Vlastimil Babka <vbabka@suse.cz> To: Eric Dumazet <eric.dumazet@gmail.com>, Andrew Morton <akpm@linux-foundation.org> Cc: Alexander Viro <viro@zeniv.linux.org.uk>, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Michal Hocko <mhocko@kernel.org>, netdev@vger.kernel.org Subject: Re: [PATCH v2] fs/select: add vmalloc fallback for select(2) Date: Tue, 27 Sep 2016 10:13:16 +0200 [thread overview] Message-ID: <6e62a278-4ac3-a866-51c6-e32511406aba@suse.cz> (raw) In-Reply-To: <1474940324.28155.44.camel@edumazet-glaptop3.roam.corp.google.com> On 09/27/2016 03:38 AM, Eric Dumazet wrote: > On Mon, 2016-09-26 at 17:01 -0700, Andrew Morton wrote: > >> I don't share Eric's concerns about performance here. If the vmalloc() >> is called, we're about to write to that quite large amount of memory >> which we just allocated, and the vmalloc() overhead will be relatively >> low. > > I did not care of the performance of this particular select() system > call really, but other cpus because of more TLB invalidations. There are many other ways to cause those, AFAIK. The reclaim/compaction for order-3 allocation has its own impact on system, including TLB flushes. Or a flood of mmap(MAP_POPULATE) and madvise(MADV_DONTNEED) calls... This vmalloc() would however require raising RLIMIT_NOFILE above the defaults. > At least CONFIG_DEBUG_PAGEALLOC=y builds should be impacted, but maybe > we do not care. I doubt anyone runs that in production, especially if performance is of concern.
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From: Vlastimil Babka <vbabka@suse.cz> To: Eric Dumazet <eric.dumazet@gmail.com>, Andrew Morton <akpm@linux-foundation.org> Cc: Alexander Viro <viro@zeniv.linux.org.uk>, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Michal Hocko <mhocko@kernel.org>, netdev@vger.kernel.org Subject: Re: [PATCH v2] fs/select: add vmalloc fallback for select(2) Date: Tue, 27 Sep 2016 10:13:16 +0200 [thread overview] Message-ID: <6e62a278-4ac3-a866-51c6-e32511406aba@suse.cz> (raw) In-Reply-To: <1474940324.28155.44.camel@edumazet-glaptop3.roam.corp.google.com> On 09/27/2016 03:38 AM, Eric Dumazet wrote: > On Mon, 2016-09-26 at 17:01 -0700, Andrew Morton wrote: > >> I don't share Eric's concerns about performance here. If the vmalloc() >> is called, we're about to write to that quite large amount of memory >> which we just allocated, and the vmalloc() overhead will be relatively >> low. > > I did not care of the performance of this particular select() system > call really, but other cpus because of more TLB invalidations. There are many other ways to cause those, AFAIK. The reclaim/compaction for order-3 allocation has its own impact on system, including TLB flushes. Or a flood of mmap(MAP_POPULATE) and madvise(MADV_DONTNEED) calls... This vmalloc() would however require raising RLIMIT_NOFILE above the defaults. > At least CONFIG_DEBUG_PAGEALLOC=y builds should be impacted, but maybe > we do not care. I doubt anyone runs that in production, especially if performance is of concern. -- 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: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2016-09-27 8:13 UTC|newest] Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-09-22 16:43 [PATCH v2] fs/select: add vmalloc fallback for select(2) Vlastimil Babka 2016-09-22 16:43 ` Vlastimil Babka 2016-09-22 16:49 ` Eric Dumazet 2016-09-22 16:49 ` Eric Dumazet 2016-09-22 16:49 ` Eric Dumazet 2016-09-22 16:56 ` Vlastimil Babka 2016-09-22 16:56 ` Vlastimil Babka 2016-09-22 17:07 ` Eric Dumazet 2016-09-22 17:07 ` Eric Dumazet 2016-09-22 17:07 ` Eric Dumazet 2016-09-22 17:55 ` Vlastimil Babka 2016-09-22 17:55 ` Vlastimil Babka 2016-09-23 9:42 ` David Laight 2016-09-23 9:58 ` Vlastimil Babka 2016-09-23 9:58 ` Vlastimil Babka 2016-09-23 9:58 ` Vlastimil Babka 2016-09-23 13:35 ` David Laight 2016-09-26 10:01 ` Vlastimil Babka 2016-09-26 10:01 ` Vlastimil Babka 2016-09-26 15:02 ` David Laight 2016-09-25 18:50 ` Andi Kleen 2016-09-25 18:50 ` Andi Kleen 2016-09-27 0:01 ` Andrew Morton 2016-09-27 0:01 ` Andrew Morton 2016-09-27 1:38 ` Eric Dumazet 2016-09-27 1:38 ` Eric Dumazet 2016-09-27 1:38 ` Eric Dumazet 2016-09-27 8:13 ` Vlastimil Babka [this message] 2016-09-27 8:13 ` Vlastimil Babka 2016-09-27 13:34 ` Eric Dumazet 2016-09-27 13:34 ` Eric Dumazet 2016-09-27 13:34 ` Eric Dumazet 2016-09-27 8:06 ` Vlastimil Babka 2016-09-27 8:06 ` Vlastimil Babka 2016-09-27 8:45 ` [PATCH v3] " Vlastimil Babka 2016-09-27 8:45 ` Vlastimil Babka 2016-09-27 10:22 ` Michal Hocko 2016-09-27 10:22 ` Michal Hocko
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