linux-kernel - Re: [PATCH 0/5] mm, slab: Make kmalloc

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Message-ID: <CAD7_sbH+1ZeHVcDWwVkWmNjCzDU4TUAN1zXWCmj1bftyU5o6TA@mail.gmail.com>
Date:   Thu, 5 Sep 2019 21:51:14 +0800
From:   Pengfei Li <lpf.vector@...il.com>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Christopher Lameter <cl@...ux.com>, penberg@...nel.org,
        rientjes@...gle.com, iamjoonsoo.kim@....com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/5] mm, slab: Make kmalloc_info[] contain all types of names

On Thu, Sep 5, 2019 at 8:25 PM Vlastimil Babka <vbabka@...e.cz> wrote:
>
> On 9/3/19 6:04 PM, Pengfei Li wrote:
> > There are three types of kmalloc, KMALLOC_NORMAL, KMALLOC_RECLAIM
> > and KMALLOC_DMA.
> >
> > The name of KMALLOC_NORMAL is contained in kmalloc_info[].name,
> > but the names of KMALLOC_RECLAIM and KMALLOC_DMA are dynamically
> > generated by kmalloc_cache_name().
> >
> > Patch1 predefines the names of all types of kmalloc to save
> > the time spent dynamically generating names.
> >
> > The other 4 patches did some cleanup work.
> >
> > These changes make sense, and the time spent by new_kmalloc_cache()
> > has been reduced by approximately 36.3%.
> >
> >                          Time spent by
> >                          new_kmalloc_cache()
> > 5.3-rc7                       66264
> > 5.3-rc7+patch                 42188
>
> Note that the caches are created only once upon boot, so I doubt that

Thank you for your comments.
Yes, kmalloc-xxx are only created at boot time.

> these time savings (is it in CPU cycles?) will be noticeable at all.

Yes, it is CPU cycles.

> But diffstat looks ok, and it avoids using kmalloc() (via kasprintf()) to
> allocate names for kmalloc(), so in that sense I think it's worthwhile
> to consider. Thanks.
>

Thanks.

> > Pengfei Li (5):
> >   mm, slab: Make kmalloc_info[] contain all types of names
> >   mm, slab_common: Remove unused kmalloc_cache_name()
> >   mm, slab: Remove unused kmalloc_size()
> >   mm, slab_common: Make 'type' is enum kmalloc_cache_type
> >   mm, slab_common: Make initializing KMALLOC_DMA start from 1
> >
> >  include/linux/slab.h |  20 ---------
> >  mm/slab.c            |   7 +--
> >  mm/slab.h            |   2 +-
> >  mm/slab_common.c     | 101 +++++++++++++++++++++++--------------------
> >  4 files changed, 59 insertions(+), 71 deletions(-)
> >
>