From: Mel Gorman <firstname.lastname@example.org> To: Christoph Lameter <email@example.com> Cc: Michal Hocko <firstname.lastname@example.org>, Joonsoo Kim <email@example.com>, Aruna Ramakrishna <firstname.lastname@example.org>, email@example.com, firstname.lastname@example.org, Mike Kravetz <email@example.com>, Pekka Enberg <firstname.lastname@example.org>, David Rientjes <email@example.com>, Andrew Morton <firstname.lastname@example.org>, Jiri Slaby <email@example.com> Subject: Re: what is the purpose of SLAB and SLUB (was: Re: [PATCH v3] mm/slab: Improve performance of gathering slabinfo) stats Date: Thu, 25 Aug 2016 11:07:07 +0100 [thread overview] Message-ID: <20160825100707.GU2693@suse.de> (raw) In-Reply-To: <alpine.DEB.firstname.lastname@example.org> On Wed, Aug 24, 2016 at 11:01:43PM -0500, Christoph Lameter wrote: > On Wed, 24 Aug 2016, Mel Gorman wrote: > > If/when I get back to the page allocator, the priority would be a bulk > > API for faster allocs of batches of order-0 pages instead of allocating > > a large page and splitting. > > > > OMG. Do we really want to continue this? There are billions of Linux > devices out there that require a reboot at least once a week. This is now > standard with certain Android phones. In our company we reboot all > machines every week because fragmentation degrades performance > significantly. We need to finally face up to it and deal with the issue > instead of continuing to produce more half ass-ed solutions. > Flipping the lid aside, there will always be a need for fast management of 4K pages. The primary use case is networking that sometimes uses high-order pages to avoid allocator overhead and amortise DMA setup. Userspace-mapped pages will always be 4K although fault-around may benefit from bulk allocating the pages. That is relatively low hanging fruit that would take a few weeks given a free schedule. Dirty tracking of pages on a 4K boundary will always be required to avoid IO multiplier effects that cannot be side-stepped by increasing the fundamental unit of allocation. Batching of tree_lock during reclaim for large files and swapping is also relatively low hanging fruit that also is doable in a week or two. A high-order per-cpu cache for SLUB to reduce zone->lock contention is also relatively low hanging fruit with the caveat it makes per_cpu_pages larger than a cache line. If you want to rework the VM to use a larger fundamental unit, track sub-units where required and deal with the internal fragmentation issues then by all means go ahead and deal with it. -- Mel Gorman SUSE Labs
next prev parent reply other threads:[~2016-08-25 10:08 UTC|newest] Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-08-17 18:20 [PATCH v3] mm/slab: Improve performance of gathering slabinfo stats Aruna Ramakrishna 2016-08-17 19:03 ` Eric Dumazet 2016-08-17 19:25 ` Aruna Ramakrishna 2016-08-18 11:52 ` Michal Hocko 2016-08-19 5:47 ` aruna.ramakrishna 2016-08-23 2:13 ` Joonsoo Kim 2016-08-23 15:38 ` what is the purpose of SLAB and SLUB (was: Re: [PATCH v3] mm/slab: Improve performance of gathering slabinfo) stats Michal Hocko 2016-08-23 15:54 ` what is the purpose of SLAB and SLUB Andi Kleen 2016-08-25 4:10 ` Christoph Lameter 2016-08-25 7:32 ` Michal Hocko 2016-08-25 19:49 ` Christoph Lameter 2016-08-24 1:15 ` what is the purpose of SLAB and SLUB (was: Re: [PATCH v3] mm/slab: Improve performance of gathering slabinfo) stats Joonsoo Kim 2016-08-24 8:05 ` Michal Hocko 2016-08-24 8:20 ` Mel Gorman 2016-08-25 4:01 ` Christoph Lameter 2016-08-25 10:07 ` Mel Gorman [this message] 2016-08-25 19:55 ` Christoph Lameter 2016-08-26 20:47 ` what is the purpose of SLAB and SLUB Andi Kleen 2016-08-29 13:44 ` Michal Hocko 2016-08-29 14:49 ` Christoph Lameter 2016-08-30 9:39 ` what is the purpose of SLAB and SLUB (was: Re: [PATCH v3] mm/slab: Improve performance of gathering slabinfo) stats Mel Gorman 2016-08-30 19:32 ` Christoph Lameter
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