[SPDK] Re: Performance impact with "enable_zerocopy_send"

Hello Charlie,

Could you add more details about the performance drop? Are you using SPDK target and/or initiator and what is payload size?
I would expect some degradation with small payloads, as written it this doc https://www.kernel.org/doc/html/v4.15/networking/msg_zerocopy.html#opportunity-and-caveats :
"MSG_ZEROCOPY is generally only effective at writes over around 10 KB. "

Best regards,
Alexey Marchuk

-----Original Message-----
From: Charlie Li <charlie.li(a)gmail.com> 
Sent: Wednesday, January 20, 2021 12:41 AM
To: Storage Performance Development Kit <spdk(a)lists.01.org>
Subject: [SPDK] Performance impact with "enable_zerocopy_send"

Hello,

In SPDK 20.10, "enable_zerocopy_send" is set to "false" by default.

I tried to set  "enable_zerocopy_send" to true, but noticed the performance dropped.

Is this as expected? My understanding is that setting "enable_zerocopy_send" to true should improve performance.

Thanks,
Charlie
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