+ Alasdair and dm-devel for awareness and inputs.
On 5/9/2017 12:26 PM, Neeraj Soni wrote:
Hi Keith/Snitzer,
I have recently started using kernel 4.4 on a Android device and ran
Androbench to check storage read/write performance. I found that the
Random Read (RR) and Random write(RW) performance with Full Disk
Encryption is degraded compared to no Disk Encryption. Initially i
thought this must the issue with the storage part used and i compared
the performance of similar storage part on a device that was using
Android with kernel 3.18. I found that with no Disk Encryption the
performance was equivalent to the device which was using 4.4 but with
Disk Encryption there was degradation in RR (~20%) and RW(10%).
I then tried to compare the changes that was brought in kernel 4.4 in
Full Disk Encryption path. I came across the patch mentioned in
subject and found that now a worker thread is scheduled in
dm_request_fn() to process the requests instead of directly invoking
map_request() as was in kernel 3.18.
I reverted this patch and found that the RR and RW performance was now
closer to what we have without Disk Encryption. From the commit
message i understand that this change is significant and will be
required for blk-mq support but have you came across such degradation
issue with your patch and do we have any fix for this degradation
available?
BR,
Neeraj Soni,
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