Re: To add, or not to add, a bio REQ_ROTATIONAL flag

[+cc from "Enable use of Solid State Hybrid Drives" https://lkml.org/lkml/2014/10/29/698 ] On Thu, 28 Jul 2016, Martin K. Petersen wrote: > > "Eric" == Eric Wheeler writes: > Eric> [...] This may imply that > Eric> we need a new way to flag cache bypass

Re: To add, or not to add, a bio REQ_ROTATIONAL flag

[+cc from "Enable use of Solid State Hybrid Drives" https://lkml.org/lkml/2014/10/29/698 ] On Thu, 28 Jul 2016, Martin K. Petersen wrote: > > "Eric" == Eric Wheeler writes: > Eric> [...] This may imply that > Eric> we need a new way to flag cache bypass from userspace [...] > Eric>

Re: To add, or not to add, a bio REQ_ROTATIONAL flag

> "Eric" == Eric Wheeler writes: Eric, Eric> However, just because FADV_SEQUENTIAL is flagged doesn't mean the Eric> cache should bypass. Filesystems can fragment, and while the file Eric> being read may be read sequentially, the blocks on which it Eric> resides

Re: To add, or not to add, a bio REQ_ROTATIONAL flag

> "Eric" == Eric Wheeler writes: Eric, Eric> However, just because FADV_SEQUENTIAL is flagged doesn't mean the Eric> cache should bypass. Filesystems can fragment, and while the file Eric> being read may be read sequentially, the blocks on which it Eric> resides may not be. Same thing for

Re: To add, or not to add, a bio REQ_ROTATIONAL flag

On 29/07/16 01:50, Eric Wheeler wrote: > Hello all, > > With the many SSD caching layers being developed (bcache, dm-cache, > dm-writeboost, etc), how could we flag a bio from userspace to indicate > whether the bio is preferred to hit spinning disks instead of an SSD? > > Unnecessary

Re: To add, or not to add, a bio REQ_ROTATIONAL flag

On 29/07/16 01:50, Eric Wheeler wrote: > Hello all, > > With the many SSD caching layers being developed (bcache, dm-cache, > dm-writeboost, etc), how could we flag a bio from userspace to indicate > whether the bio is preferred to hit spinning disks instead of an SSD? > > Unnecessary