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Bug 4941 - ALSA: excessive IO causes high CPU usage
Summary: ALSA: excessive IO causes high CPU usage
Status: RESOLVED FIXED
Alias: None
Product: SDL
Classification: Unclassified
Component: audio (show other bugs)
Version: HG 1.2
Hardware: All Linux
: P2 normal
Assignee: Ryan C. Gordon
QA Contact: Sam Lantinga
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2020-01-13 18:08 UTC by Paul Cercueil
Modified: 2020-06-24 22:30 UTC (History)
1 user (show)

See Also:

Attachments
Patch to fix the issue (1.75 KB, text/plain)
2020-01-13 18:08 UTC, Paul Cercueil 		Details
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Description Paul Cercueil 2020-01-13 18:08:12 UTC 
Created attachment 4157 [details]
Patch to fix the issue

Quote from the patch:

"On GCW Zero jz4770 platform, I saw higher than usual CPU usage when
running a more recent kernel (4.xx series versus 3.xx). Upon
investigation, it was found that the ALSA pcm file was not blocking
as it should. This resulted in ~30-50,000 system calls a second that
were unnecesary.

After adjusting the order in which SDL requests its pcm blocking mode,
the number of syscalls a second has dropped to a much smaller figure,
< 1,000/sec if I recall correctly. CPU usage also dropped by ~5%."
Comment 1 Ryan C. Gordon 2020-03-23 02:04:35 UTC 
Generally we don't mess with SDL 1.2, but this patch was straightforward enough that I've applied it to revision control here: https://hg.libsdl.org/SDL/rev/9c0fc6e28c5e

--ryan.
Comment 2 Ozkan Sezer 2020-06-24 22:30:11 UTC 
Does the default/2.0 branch not need this change?