From: Alexey Dobriyan <adobriyan@gmail.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] proc: calculate end pointer for /proc/*/* lookup at compile time
Date: Wed, 30 Jan 2019 08:55:01 +0300 [thread overview]
Message-ID: <20190130055501.GA2115@avx2> (raw)
In-Reply-To: <20190129141848.5f3d2d1aa125c8ec45ee091d@linux-foundation.org>
On Tue, Jan 29, 2019 at 02:18:48PM -0800, Andrew Morton wrote:
> On Mon, 14 Jan 2019 23:04:23 +0300 Alexey Dobriyan <adobriyan@gmail.com> wrote:
>
> > Compilers like to transform loops like
> >
> > for (i = 0; i < n; i++) {
> > [use p[i]]
> > }
> >
> > into
> > for (p = p0; p < end; p++) {
> > ...
> > }
> >
> > Do it by hand, so that it results in overall simpler loop
> > and smaller code.
> >
> > Space savings:
> >
> > $ ./scripts/bloat-o-meter ../vmlinux-001 ../obj/vmlinux
> > add/remove: 0/0 grow/shrink: 2/1 up/down: 4/-9 (-5)
> > Function old new delta
> > proc_tid_base_lookup 17 19 +2
> > proc_tgid_base_lookup 17 19 +2
> > proc_pident_lookup 179 170 -9
> >
> > Note: this trick bloats readdir, so don't do it :-\
>
> I don't understand the Note:. Can you please expand?
The same could be done to proc_pident_readdir(), but the code becomes
bigger for some reason.
prev parent reply other threads:[~2019-01-30 5:55 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-14 20:04 [PATCH] proc: calculate end pointer for /proc/*/* lookup at compile time Alexey Dobriyan
2019-01-29 22:18 ` Andrew Morton
2019-01-30 5:55 ` Alexey Dobriyan [this message]
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