Re: [PATCH v3 4/4] scsi: target: return COMPARE AND WRITE miscompare offsets

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Fri, 30 Oct 2020 20:06:31 -0400, Douglas Gilbert wrote:

> I believe the logic is correct (and scsi_debug doesn't set the INFO field
> in its CAW, but should), but I wonder about performance.
> 
> If the probability of equality is high (e.g. like it is usually with
> VERIFY(BytChk=1) ) and memcmp() is faster than that for-loop (which
> could be optimized), then a better strategy might be to always do memcmp()
> first and only if it fails go into the byte by byte for-loop to find the
> offset of the first miscompare.

While adding the INFO return to tgt I noticed that it had the same
memcmp-with-miscompare-for-loop logic that you describe. I'm only aware
of ESXi as a COMPARE AND WRITE consumer and I think probability of
equality is quite high (@Dirk: perhaps you can confirm?).

> IMO this should only be considered, if there is going to be a "v4" of
> this patchset.

I think this optimization wouldn't make the code much more complex, so
I'll do a re-spin with this change. Thanks for the feedback.

Cheers, David



[Index of Archives]     [Linux SCSI]     [Kernel Newbies]     [Linux SCSI Target Infrastructure]     [Share Photos]     [IDE]     [Security]     [Git]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Linux ATA RAID]     [Linux IIO]     [Device Mapper]

  Powered by Linux