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authorVineet Gupta <vgupta@synopsys.com>2019-05-14 16:28:30 -0700
committerVineet Gupta <vgupta@synopsys.com>2019-07-01 11:02:22 -0700
commit926150db8558dca59617c8786c3f91c239290ee1 (patch)
tree8d660572a26f911350adffca3bc37a3ba239f8f9 /arch/arc/include
parent5e91bf5ce9b8740076f5283f1ec3a5b023950920 (diff)
downloadlinux-926150db8558dca59617c8786c3f91c239290ee1.tar.gz
ARC: mm: do_page_fault refactor #8: release mmap_sem sooner
In case of successful page fault handling, this patch releases mmap_sem before updating the perf stat event for major/minor faults. So even though the contention reduction is NOT super high, it is still an improvement. There's an additional code size improvement as we only have 2 up_read() calls now. Note to myself: -------------- 1. Given the way it is done, we are forced to move @bad_area label earlier causing the various "goto bad_area" cases to hit perf stat code. - PERF_COUNT_SW_PAGE_FAULTS is NOW updated for access errors which is what arm/arm64 seem to be doing as well (with slightly different code) - PERF_COUNT_SW_PAGE_FAULTS_{MAJ,MIN} must NOT be updated for the error case which is guarded by now setting @fault initial value to VM_FAULT_ERROR which serves both cases when handle_mm_fault() returns error or is not called at all. 2. arm/arm64 use two homebrew fault flags VM_FAULT_BAD{MAP,MAPACCESS} which I was inclined to add too but seems not needed for ARC - given that we have everything is 1 function we can still use goto - we setup si_code at the right place (arm* do that in the end) - we init fault already to error value which guards entry into perf stats event update Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
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