Re: [PATCH RESEND v2 1/1] fix a dead loop when in heavy low memory

[Greg KH]

On Sun, Dec 27, 2015 at 05:14:51PM +0800, Figo Zhang wrote:
> Android System UI hang when run heavy monkey stress test.
> 
> V2: add more detail about how to re-produce this issue, the
> important is install more than 100 apps/games.
> 
> Re-produce step:
> Run this monkey stress test script with more than 100
> apps/games installed:
> 
> adb shell "monkey --ignore-crashes --ignore-timeouts
> --kill-process-after-error --ignore-security-exceptions
> --throttle 200 -v 20000000"
> 
> kernel log:
> [ 1526.272125] lowmem_scan start: 128, 213da, ofree -9849 34419, ma 529
> [ 1526.272260] lowmemorykiller: select 'dTi-lm' (27289), adj 647, size 10630, to kill
> [ 1526.272299] lowmem_d_timeout=4296194081
> [ 1526.272303] Killing 'dTi-lm' (27289), adj 647,
> [ 1526.272303]    to free 42520kB on behalf of 'servicemanager' (2365) because
> [ 1526.272303]    cache 137676kB is below limit 221184kB for oom_score_adj 529
> [ 1526.272303]    Free memory is -39396kB above reserved
> [ 1526.272304] lowmem_scan end: 128, 213da, return 10630
> [ 1526.272710] lowmem_scan start: 128, 213da, ofree -9849 34373, ma 529
> [ 1526.272832] lowmem: TIF_MEMDIE, adj=647, dTi-lm, jiffies=4296193081, 4296194081
> [ 1526.274450] lowmem_scan start: 128, 280da, ofree -9601 34327, ma 529
> [ 1526.274695] lowmem: TIF_MEMDIE, adj=647, dTi-lm, jiffies=4296193083, 4296194081
> [ 1526.282292] lowmem_scan start: 128, 213da, ofree -9703 34327, ma 529
> [ 1526.282727] lowmem: TIF_MEMDIE, adj=647, dTi-lm, jiffies=4296193090, 4296194081
> [ 1526.316888] lowmem_scan start: 128, 213da, ofree -9766 34465, ma 529
> [ 1526.317019] lowmem: TIF_MEMDIE, adj=647, dTi-lm, jiffies=4296193125, 4296194081
> [ 1526.319311] lowmem_scan start: 128, 213da, ofree -9856 34419, ma 529
> [ 1526.319442] lowmem: TIF_MEMDIE, adj=647, dTi-lm, jiffies=4296193125, 4296194081
> [ 1526.322026] lowmem_scan start: 128, 280da, ofree -9841 34327, ma 529
> [ 1526.360831] lowmem: TIF_MEMDIE, adj=647, dTi-lm, jiffies=4296193166, 4296194081
> [ 1526.532233] lowmem_scan start: 128, 213da, ofree -9846 34511, ma 529
> [ 1526.644046] lowmem_scan start: 128, 213da, ofree -9785 34235, ma 529
> [ 1527.437578] lowmem: TIF_MEMDIE, adj=647, dTi-lm, jiffies=4296194246, 4296195109
> [ 1527.442559] lowmem_scan start: 128, 213da, ofree -9850 41884, ma 529
> [ 1527.459540] lowmem: TIF_MEMDIE, adj=647, dTi-lm, jiffies=4296194268, 4296195109
> [ 1527.500352] lowmem: TIF_MEMDIE, adj=647, dTi-lm, jiffies=4296194309, 4296195109
> 
> when this happened, the android system UI will hang, no process can be
> select to kill.
> 
> i found the the value of "lowmem_deathpending_timeout" will be modified
> strangely, like in last killing, the value is 4296194081, but why not it
> had changed to 4296195109? so it will cause the deadloop in low memory
> state which will cause the android system UI hang, because no process will
>  be kill.
> 
> commit e5d7965f88a3 ("staging: android: lowmemorykiller: Don't wait more
> than one second for a process to die") said wait 1 seconds, i think it no
> need to wait 1 second, because we don't select the process with
> "TIF_MEMDIE" to kill.
> 
> Signed-off-by: Figo Zhang <tianfei.zhang@xxxxxxxxx>

As you ignored my instructions to you, I'm going to just ignore this
patch, sorry.  Now discarded.

greg k-h
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