On Mon, Sep 25, 2017 at 02:24:46PM +0800, Huang, Ying wrote: > Minchan Kim <minchan@xxxxxxxxxx> writes: > > > On Mon, Sep 25, 2017 at 01:54:42PM +0800, Huang, Ying wrote: > >> Hi, Minchan, > >> > >> Minchan Kim <minchan@xxxxxxxxxx> writes: > >> > >> > Hi Huang, > >> > > >> > On Thu, Sep 21, 2017 at 09:33:10AM +0800, Huang, Ying wrote: > >> >> From: Huang Ying <ying.huang@xxxxxxxxx> > >> > >> [snip] > >> > >> >> diff --git a/mm/Kconfig b/mm/Kconfig > >> >> index 9c4bdddd80c2..e62c8e2e34ef 100644 > >> >> --- a/mm/Kconfig > >> >> +++ b/mm/Kconfig > >> >> @@ -434,6 +434,26 @@ config THP_SWAP > >> >> > >> >> For selection by architectures with reasonable THP sizes. > >> >> > >> >> +config VMA_SWAP_READAHEAD > >> >> + bool "VMA based swap readahead" > >> >> + depends on SWAP > >> >> + default y > >> >> + help > >> >> + VMA based swap readahead detects page accessing pattern in a > >> >> + VMA and adjust the swap readahead window for pages in the > >> >> + VMA accordingly. It works better for more complex workload > >> >> + compared with the original physical swap readahead. > >> >> + > >> >> + It can be controlled via the following sysfs interface, > >> >> + > >> >> + /sys/kernel/mm/swap/vma_ra_enabled > >> >> + /sys/kernel/mm/swap/vma_ra_max_order > >> > > >> > It might be better to discuss in other thread but if you mention new > >> > interface here again, I will discuss it here. > >> > > >> > We are creating new ABI in here so I want to ask question in here. > >> > > >> > Did you consier to use /sys/block/xxx/queue/read_ahead_kb for the > >> > swap readahead knob? Reusing such common/consistent knob would be better > >> > than adding new separate konb. > >> > >> The problem is that the configuration of VMA based swap readahead is > >> global instead of block device specific. And because it works in > >> virtual way, that is, the swap blocks on the different block devices may > >> be readahead together. It's a little hard to use the block device > >> specific configuration. > > > > Fair enough. page-cluster from the beginning should have been like that > > instead of vma_ra_max_order. > > > > One more questions: Do we need separate vma_ra_enable? > > > > Can't we disable it via echo 0 > /sys/kernel/mm/swap/vma_ra_max_order > > like page-cluster? > > The difference is, > > vma_ra_eanble: 0 > => use original physical swap readahead > > vma_ra_enable: 1 && vma_ra_max_order: 0 > => use VMA based swap readahead and disable the readahead. I understand now. Thanks! -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
