From: Xiongwei Song <sxwjean@gmail.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Xiongwei Song <sxwjean@me.com>,
cl@linux.com, penberg@kernel.org, rientjes@google.com,
iamjoonsoo.kim@lge.com, akpm@linux-foundation.org,
vbabka@suse.cz, linux-mm@kvack.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm: append __GFP_COMP flag for trace_malloc
Date: Wed, 28 Apr 2021 11:05:18 +0800 [thread overview]
Message-ID: <CAEVVKH8AFMqwEcpp=7h7k-_BYqwU+gutoUMNM93pnGPiW=u+gg@mail.gmail.com> (raw)
In-Reply-To: <20210427112527.GX235567@casper.infradead.org>
On Tue, Apr 27, 2021 at 7:26 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Tue, Apr 27, 2021 at 01:30:48PM +0800, Xiongwei Song wrote:
> > Hi Mattew,
> >
> > One more thing I should explain, the kmalloc_order() appends the
> > __GFP_COMP flags,
> > not by the caller.
> >
> > void *kmalloc_order(size_t size, gfp_t flags, unsigned int order)
> > {
> > ...........................................................
> >
> > flags |= __GFP_COMP;
> > page = alloc_pages(flags, order);
> > ...........................................................
> > return ret;
> > }
> > EXPORT_SYMBOL(kmalloc_order);
> >
> > #ifdef CONFIG_TRACING
> > void *kmalloc_order_trace(size_t size, gfp_t flags, unsigned int order)
> > {
> > void *ret = kmalloc_order(size, flags, order);
> > trace_kmalloc(_RET_IP_, ret, size, PAGE_SIZE << order, flags);
> > return ret;
> > }
> > EXPORT_SYMBOL(kmalloc_order_trace);
> > #endif
>
> Yes, I understood that. What I don't understand is why appending the
> __GFP_COMP to the trace would have been less confusing for you.
>
> Suppose I have some code which calls:
>
> kmalloc(10 * 1024, GFP_ATOMIC|__GFP_NOWARN|__GFP_NOMEMALLOC);
>
> and I see in my logs
>
> 0.08% call_site=ffffffff851d0cb0 ptr=0xffff8c04a4ca0000 bytes_req=10176 bytes_alloc=16384 gfp_flags=GFP_ATOMIC|__GFP_NOWARN|__GFP_NOMEMALLOC|__GFP_COMP
>
> That seems to me _more_ confusing because I would wonder "Where did that
> __GFP_COMP come from?"
Thank you for the comments. But I disagree.
When I use trace, I hope I can get the precise data rather than something
changed that I don't know , then I can get the correct conclusion or
direction on my issue.
Here my question is what the trace events are for if they don't provide the
real situation? I think that's not graceful and friendly.
From my perspective, it'd be better to know my flags changed before checking
code lines one by one. In other words, I need a warning to reminder me on this,
then I can know quickly my process might do some incorrect things.
Regards,
Xiongwei
next prev parent reply other threads:[~2021-04-28 3:05 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-27 2:43 [PATCH] mm: append __GFP_COMP flag for trace_malloc Xiongwei Song
2021-04-27 2:53 ` Matthew Wilcox
2021-04-27 3:29 ` Xiongwei Song
2021-04-27 3:36 ` Matthew Wilcox
2021-04-27 4:11 ` Xiongwei Song
2021-04-27 5:30 ` Xiongwei Song
2021-04-27 11:25 ` Matthew Wilcox
2021-04-28 3:05 ` Xiongwei Song [this message]
2021-05-03 12:35 ` Vlastimil Babka
2021-05-07 5:41 ` Xiongwei Song
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAEVVKH8AFMqwEcpp=7h7k-_BYqwU+gutoUMNM93pnGPiW=u+gg@mail.gmail.com' \
--to=sxwjean@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=cl@linux.com \
--cc=iamjoonsoo.kim@lge.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=penberg@kernel.org \
--cc=rientjes@google.com \
--cc=sxwjean@me.com \
--cc=vbabka@suse.cz \
--cc=willy@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).