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From: | Jeff Moyer |
Subject: | Re: [Qemu-devel] [PATCH v5 1/6] libnvdimm: nd_region flush callback support |
Date: | Fri, 12 Apr 2019 09:12:10 -0400 |
User-agent: | Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) |
Jan Kara <address@hidden> writes: > On Thu 11-04-19 07:51:48, Dan Williams wrote: >> On Tue, Apr 9, 2019 at 9:09 PM Pankaj Gupta <address@hidden> wrote: >> > + } else { >> > + if (nd_region->flush(nd_region)) >> > + rc = -EIO; >> >> Given the common case wants to be fast and synchronous I think we >> should try to avoid retpoline overhead by default. So something like >> this: >> >> if (nd_region->flush == generic_nvdimm_flush) >> rc = generic_nvdimm_flush(...); > > I'd either add a comment about avoiding retpoline overhead here or just > make ->flush == NULL mean generic_nvdimm_flush(). Just so that people don't > get confused by the code. Isn't this premature optimization? I really don't like adding things like this without some numbers to show it's worth it. -Jeff
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