Hello, On 26.11.2019 16:52, Josef Bacik wrote: > On Tue, Nov 26, 2019 at 03:41:30PM +0100, Mikhail Zaslonko wrote: >> Due to the small size of zlib buffer (1 page) set in btrfs code, s390 >> hardware compression is rather limited in terms of performance. Increasing >> the buffer size to 4 pages would bring significant benefit for s390 >> hardware compression (up to 60% better performance compared to the >> PAGE_SIZE buffer) and should not bring much overhead in terms of memory >> consumption due to order 2 allocations. >> >> Signed-off-by: Mikhail Zaslonko <zaslonko@xxxxxxxxxxxxx> > > We may have to make these allocations under memory pressure in the IO context, > order 2 allocations here is going to be not awesome. If you really want it then > you need to at least be able to fall back to single page if you fail to get the > allocation. Thanks, > As far as I understand GFP_KERNEL allocations would never fail for the order <= PAGE_ALLOC_COSTLY_ORDER. How else can the memory pressure condition be identified here? > josef >
