From: David Laight <David.Laight@ACULAB.COM>
To: 'Mel Gorman' <mgorman@techsingularity.net>,
Michal Hocko <mhocko@suse.com>
Cc: Linux-MM <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>,
NeilBrown <neilb@suse.de>,
Thierry Reding <thierry.reding@gmail.com>,
"Matthew Wilcox" <willy@infradead.org>,
Vlastimil Babka <vbabka@suse.cz>,
LKML <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH 2/7] mm/page_alloc: Treat RT tasks similar to __GFP_HIGH
Date: Fri, 13 Jan 2023 09:04:50 +0000 [thread overview]
Message-ID: <4c169ca43a7b49f1bf61c01181ed585e@AcuMS.aculab.com> (raw)
In-Reply-To: <20230112093623.sl4jpqf6f2ng43w2@techsingularity.net>
From: Mel Gorman
> Sent: 12 January 2023 09:36
...
> Hard realtime tasks should be locking down resources in advance. Even a
> soft-realtime task like audio or video live decoding which cannot jitter
> should be allocating both memory and any disk space required up-front
> before the recording starts instead of relying on reserves. At best,
> reserve access will only delay the problem by a very short interval.
Or, at least, ensuring the system isn't memory limited.
The biggest effect on RT task latency/jitter (on a normal kernel)
is hardware interrupt and softint code 'stealing' the cpu.
The main 'culprit' being ethernet receive.
Unfortunately if you are doing RTP audio (UDP data) you absolutely
need the ethernet receive to run. When the softint code decides
to drop back to a normal priority kernel worker thread packets
get lost.
(I've been running 10000 RTP streams - with 10k receive UDP sockets.)
So I doubt avoiding sleeps in kmalloc() is going to make a
significant difference.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2023-01-13 9:05 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-09 15:16 [PATCH 0/6 v2] Discard __GFP_ATOMIC Mel Gorman
2023-01-09 15:16 ` [PATCH 1/7] mm/page_alloc: Rename ALLOC_HIGH to ALLOC_MIN_RESERVE Mel Gorman
2023-01-11 15:18 ` Michal Hocko
2023-01-12 9:26 ` Mel Gorman
2023-01-09 15:16 ` [PATCH 2/7] mm/page_alloc: Treat RT tasks similar to __GFP_HIGH Mel Gorman
2023-01-11 15:27 ` Michal Hocko
2023-01-12 9:36 ` Mel Gorman
2023-01-12 9:47 ` Michal Hocko
2023-01-12 16:42 ` Mel Gorman
2023-01-13 9:04 ` David Laight [this message]
2023-01-13 11:09 ` Mel Gorman
2023-01-09 15:16 ` [PATCH 3/7] mm/page_alloc: Explicitly record high-order atomic allocations in alloc_flags Mel Gorman
2023-01-10 15:28 ` Vlastimil Babka
2023-01-11 15:36 ` Michal Hocko
2023-01-12 9:38 ` Mel Gorman
2023-01-09 15:16 ` [PATCH 4/7] mm/page_alloc: Explicitly define what alloc flags deplete min reserves Mel Gorman
2023-01-11 14:04 ` Vlastimil Babka
2023-01-11 15:37 ` Michal Hocko
2023-01-09 15:16 ` [PATCH 5/7] mm/page_alloc.c: Allow __GFP_NOFAIL requests deeper access to reserves Mel Gorman
2023-01-11 14:05 ` Vlastimil Babka
2023-01-11 15:46 ` Michal Hocko
2023-01-12 9:43 ` Mel Gorman
2023-01-09 15:16 ` [PATCH 6/7] mm/page_alloc: Give GFP_ATOMIC and non-blocking allocations " Mel Gorman
2023-01-11 14:12 ` Vlastimil Babka
2023-01-11 15:58 ` Michal Hocko
2023-01-11 17:05 ` Mel Gorman
2023-01-12 8:11 ` Michal Hocko
2023-01-12 8:29 ` Michal Hocko
2023-01-12 9:24 ` Mel Gorman
2023-01-12 9:45 ` Michal Hocko
2023-01-14 22:10 ` NeilBrown
2023-01-16 10:29 ` Mel Gorman
2023-01-09 15:16 ` [PATCH 7/7] mm: discard __GFP_ATOMIC Mel Gorman
2023-01-12 8:12 ` Michal Hocko
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