linux-kernel - Re: [PATCH v3 00/35] Memory allocation profiling

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Message-ID: <CAJuCfpEbdC4k=4aeEO=YfX2tZhkdOVaehAv9Ts7S42B_bmm=Ow@mail.gmail.com>
Date: Wed, 14 Feb 2024 12:30:49 -0800
From: Suren Baghdasaryan <surenb@...gle.com>
To: Yosry Ahmed <yosryahmed@...gle.com>
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Subject: Re: [PATCH v3 00/35] Memory allocation profiling

On Wed, Feb 14, 2024 at 12:17 PM Yosry Ahmed <yosryahmed@...gle.com> wrote:
>
> > > > Performance overhead:
> > > > To evaluate performance we implemented an in-kernel test executing
> > > > multiple get_free_page/free_page and kmalloc/kfree calls with allocation
> > > > sizes growing from 8 to 240 bytes with CPU frequency set to max and CPU
> > > > affinity set to a specific CPU to minimize the noise. Below are results
> > > > from running the test on Ubuntu 22.04.2 LTS with 6.8.0-rc1 kernel on
> > > > 56 core Intel Xeon:
> > > >
> > > >                         kmalloc                 pgalloc
> > > > (1 baseline)            6.764s                  16.902s
> > > > (2 default disabled)    6.793s (+0.43%)         17.007s (+0.62%)
> > > > (3 default enabled)     7.197s (+6.40%)         23.666s (+40.02%)
> > > > (4 runtime enabled)     7.405s (+9.48%)         23.901s (+41.41%)
> > > > (5 memcg)               13.388s (+97.94%)       48.460s (+186.71%)
> >
> > (6 default disabled+memcg)    13.332s (+97.10%)         48.105s (+184.61%)
> > (7 default enabled+memcg)     13.446s (+98.78%)       54.963s (+225.18%)
>
> I think these numbers are very interesting for folks that already use
> memcg. Specifically, the difference between 6 & 7, which seems to be
> ~0.85% and ~14.25%. IIUC, this means that the extra overhead is
> relatively much lower if someone is already using memcgs.

Well, yes, percentage-wise it's much lower. If you look at the
absolute difference between 6 & 7 vs 2 & 3, it's quite close.

>
> >
> > (6) shows a bit better performance than (5) but it's probably noise. I
> > would expect them to be roughly the same. Hope this helps.
> >
> > > >
> > >
> > >