> -----Original Message----- > From: linux-raid-owner@xxxxxxxxxxxxxxx [mailto:linux-raid- > owner@xxxxxxxxxxxxxxx] On Behalf Of kedacomkernel > Sent: Tuesday, August 21, 2012 6:26 PM > To: Dan Williams; majianpeng > Cc: Neil Brown; linux-raid > Subject: Re: Re: raid5: When add stripe_head to inactive_list, it should > remove hash. > > On 2012-08-22 00:43 Dan Williams <djbw@xxxxxx> Wrote: > >On Mon, Aug 20, 2012 at 8:14 PM, Jianpeng Ma <majianpeng@xxxxxxxxx> > wrote: > >> On 2012-08-21 01:51 Dan Williams <djbw@xxxxxx> Wrote: > >>>On Mon, Aug 20, 2012 at 1:17 AM, Jianpeng Ma > <majianpeng@xxxxxxxxx> wrote: > >>>> I think step4 maybe return ioerror.But it's success. > >>> > >>>You would need to check that stripe0 got recycled between step2 and > >>>step3. If not then the uptodate stripe is in the cache and the read > >>>can be serviced from the cached data. > >>> > >>>...which seems to be the case because of: > >>> > >>>> [19277.585936] locked=0 uptodate=4 to_read=0 to_write=0 failed=1 > >>>> failed_num=3,-1 > >>> > >> > >> Thanks! If stripe had a cache function.I think the chunk_aligned_read > should use it for small read situation. > > > >But the stripe cache is not meant to be a read cache as it would be > >duplicating what the page cache offers. Most aligned reads are likely > >to miss the stripe cache so adding a lookup for every read would be > >mostly wasted overhead. > > > I think most aligned reads are likely to missed the stripe cache because they > did not use stripe-cache(when fristly reaed) For direct-io workload, there is > no page-cache. > FYI, most hardware raid-controlers have own memory and don't use host- > memeory. The stripe-cache of raid456 is the same as raid-controller > memeory.They also should provide the page-cache for read, rather only for > write. So if a portion of the system memory can be battery backed (something like the ADR feature on the Intel Xeon E5 series), would it be possible for us to put the stripe cache in that battery protected region and make it a protected write back cache to improve performance and provide data protection for software RAID on Linux? ��.n��������+%������w��{.n�����{����w��ܨ}���Ơz�j:+v�����w����ޙ��&�)ߡ�a����z�ޗ���ݢj��w�f
