From: Jared Hu <jared.hu@nxp.com>
To: "linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: question for cma alloc fail issue
Date: Tue, 19 Mar 2019 08:31:37 +0000 [thread overview]
Message-ID: <DB7PR04MB55808491855429C48CE8CCF298400@DB7PR04MB5580.eurprd04.prod.outlook.com> (raw)
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Hi All，
We are facing a cma memory alloc issue. In our platform imx8m, we using cma to allocate large continuous memory block to support zero-copy between video decode and display sub-system. But after long time loop video playback test, system will report alloc cma fail ret=busy.
We take a deep look into cma.c found there are still some big free areas in cma->bitmap that maybe can meet the required 3595 pages.
The question is pages that are free in cma->bitmap seem not free in Buddy system? Then which one maybe occupy these pages? We suspect these pages are file cache because if drop all cache, then this issue will not happen.
We have two clues as below:
1. PageBuddy test fail even if the page is 0 in bitmap
Eg, page 117760 located in 10274@115678, PageBuddy() will return false as below log show:
multiqueue1542:-8444 [003] d..1 225233.624057: test_pages_isolated: pfn 0x60c00 pageBuddy return false
multiqueue1542:-8444 [003] d..1 225233.624058: test_pages_isolated: return pfn=0x60c00
below is the cma area bitmap summary when error occurs, there are still some big areas in yellow marks which can hold 3595 pages:
cma_alloc: alloc failed, req-size: 3595 pages, ret: -16
cma_alloc: number of available pages:
4@8420+18@8430+80@8880+129@74623+1023@78849+34@82910+6178@85982+34@95198+8226@98270+34@109534+34@112606
+10274@115678+1058@128990+34@133086+34@136158+2082@139230+9250@144350+34@156638+1570@159710+9762@164318
+2549@177675+19957@183819+5621@207371+12789@216587+245@232971+245@236811+245@240651+1269@244491 => 92812 free of 245760 total pages
2. Meanwhile in debuf fs the free size is not aligned with that meminfo reported:
In debuf fs: 245760-138568=107192(pages) = 428768 kB
In /proc/meminfo: 296976 kB
root@imx8mqevk:~# cat /proc/meminfo | grep Cma*
CmaTotal: 983040 kB
CmaFree: 296976 kB
root@imx8mqevk:~# cat /sys/kernel/debug/cma/cma-linux,cma/count
245760
root@imx8mqevk:~# cat /sys/kernel/debug/cma/cma-linux,cma/used
138568
Could someone give me a favor to debug this issue?
Best regards
Jared Hu
Mobile: 86-15962100482
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next reply other threads:[~2019-03-19 8:31 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-19 8:31 Jared Hu [this message]
2019-04-10 10:48 Jared Hu
2019-04-10 13:14 ` Matthew Wilcox
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