From: Pekka Enberg <penberg@iki.fi>
To: Michal Hocko <mhocko@kernel.org>, "Tobin C. Harding" <me@tobin.cc>
Cc: Vlastimil Babka <vbabka@suse.cz>,
"Tobin C. Harding" <tobin@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Christoph Lameter <cl@linux.com>,
Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>, Tejun Heo <tj@kernel.org>,
Qian Cai <cai@lca.pw>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Mel Gorman <mgorman@techsingularity.net>
Subject: Re: [PATCH 0/1] mm: Remove the SLAB allocator
Date: Thu, 11 Apr 2019 11:27:26 +0300 [thread overview]
Message-ID: <262df687-c934-b3e2-1d5f-548e8a8acb74@iki.fi> (raw)
In-Reply-To: <20190411075556.GO10383@dhcp22.suse.cz>
Hi,
On 4/11/19 10:55 AM, Michal Hocko wrote:
> Please please have it more rigorous then what happened when SLUB was
> forced to become a default
This is the hard part.
Even if you are able to show that SLUB is as fast as SLAB for all the
benchmarks you run, there's bound to be that one workload where SLUB
regresses. You will then have people complaining about that (rightly so)
and you're again stuck with two allocators.
To move forward, I think we should look at possible *pathological* cases
where we think SLAB might have an advantage. For example, SLUB had much
more difficulties with remote CPU frees than SLAB. Now I don't know if
this is the case, but it should be easy to construct a synthetic
benchmark to measure this.
For example, have a userspace process that does networking, which is
often memory allocation intensive, so that we know that SKBs traverse
between CPUs. You can do this by making sure that the NIC queues are
mapped to CPU N (so that network softirqs have to run on that CPU) but
the process is pinned to CPU M.
It's, of course, worth thinking about other pathological cases too.
Workloads that cause large allocations is one. Workloads that cause lots
of slab cache shrinking is another.
- Pekka
next prev parent reply other threads:[~2019-04-11 8:27 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-10 2:47 [PATCH 0/1] mm: Remove the SLAB allocator Tobin C. Harding
2019-04-10 2:47 ` [PATCH 1/1] mm: Remove " Tobin C. Harding
2019-04-10 8:02 ` [PATCH 0/1] mm: Remove the " Vlastimil Babka
2019-04-10 8:16 ` Tobin C. Harding
2019-04-11 7:55 ` Michal Hocko
2019-04-11 8:27 ` Pekka Enberg [this message]
2019-04-17 8:50 ` Jesper Dangaard Brouer
2019-04-17 13:27 ` Christopher Lameter
2019-04-17 13:38 ` Michal Hocko
2019-04-22 14:43 ` Jesper Dangaard Brouer
2019-04-11 8:44 ` Mel Gorman
2019-04-10 21:53 ` David Rientjes
2019-04-12 11:28 ` Mel Gorman
2019-04-17 3:52 ` Andrew Morton
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