From: Pavel Emelyanov <xemul@parallels•com>
To: Eric Dumazet <eric.dumazet@gmail•com>
Cc: David Miller <davem@davemloft•net>, Mel Gorman <mgorman@suse•de>,
Linux Netdev List <netdev@vger•kernel.org>,
stable@kernel•org, Alexey Kuznetsov <kuznet@ms2•inr.ac.ru>
Subject: Re: [PATCH] skb: Propagate pfmemalloc on skb from head page only
Date: Thu, 14 Mar 2013 18:23:46 +0400 [thread overview]
Message-ID: <5141DD72.6030906@parallels.com> (raw)
In-Reply-To: <1363270569.29475.11.camel@edumazet-glaptop>
>> That said, here's the proper page->pfmemalloc propagation onto socket: we
>> must check the huge-page's head page only, other pages' pfmemalloc and mapping
>> values do not contain what is expected in this place. However, I'm not sure
>> whether this fix is _complete_, since pfmemalloc propagation via lo also
>> oesn't look great.
>>
>> Both, bit propagation from page to skb and this check in sk_filter, were
>> introduced by c48a11c7 (netvm: propagate page->pfmemalloc to skb), in v3.5 so
>> Mel and stable@ are in Cc.
>>
>> Signed-off-by: Pavel Emelyanov <xemul@parallels•com>
>>
>> ---
>>
>> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
>> index eb2106f..4e525eb 100644
>> --- a/include/linux/skbuff.h
>> +++ b/include/linux/skbuff.h
>> @@ -1292,11 +1292,13 @@ static inline void __skb_fill_page_desc(struct sk_buff *skb, int i,
>> * do not lose pfmemalloc information as the pages would not be
>> * allocated using __GFP_MEMALLOC.
>> */
>> - if (page->pfmemalloc && !page->mapping)
>> - skb->pfmemalloc = true;
>> frag->page.p = page;
>> frag->page_offset = off;
>> skb_frag_size_set(frag, size);
>> +
>> + page = compound_head(page);
>> + if (page->pfmemalloc && !page->mapping)
>> + skb->pfmemalloc = true;
>> }
>>
>> /**
>> --
>
> This looks a nice finding.
>
> Note this can trigger even without vmsplice() use but regular network
> receive.
Presumably you're right, but I don't understand how :( In order to trigger
this, we should have a huge page, that gets linked to an skb _before_ it
enters the TCP receive path. How can this happen when doing sendmsg/recvmsg?
> Acked-by: Eric Dumazet <edumazet@google•com>
>
> When I discussed with David on this issue, I said that one possibility
> would be to accept a pfmemalloc skb on regular skb if no other packet is
> in a receive queue, to get a chance to make progress (and limit memory
> consumption to no more than one skb per TCP socket)
Thanks,
Pavel
next prev parent reply other threads:[~2013-03-14 14:25 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-14 13:29 [PATCH] skb: Propagate pfmemalloc on skb from head page only Pavel Emelyanov
2013-03-14 14:16 ` Eric Dumazet
2013-03-14 14:23 ` Pavel Emelyanov [this message]
2013-03-14 14:34 ` Eric Dumazet
2013-03-14 14:36 ` Pavel Emelyanov
2013-03-14 15:54 ` David Miller
2013-03-14 14:28 ` Mel Gorman
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=5141DD72.6030906@parallels.com \
--to=xemul@parallels$(echo .)com \
--cc=davem@davemloft$(echo .)net \
--cc=eric.dumazet@gmail$(echo .)com \
--cc=kuznet@ms2$(echo .)inr.ac.ru \
--cc=mgorman@suse$(echo .)de \
--cc=netdev@vger$(echo .)kernel.org \
--cc=stable@kernel$(echo .)org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
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