On Fri, Mar 04 2016, Christoph Hellwig wrote:
> This adds a flag that tells the file system that this is a high priority
> request for which it's worth to poll the hardware. The flag is purely
> advisory and can be ignored if not supported.
Here you say the flag is "advice".
>
> +/* flags for preadv2/pwritev2: */
> +#define RWF_HIPRI 0x00000001 /* high priority request, poll if possible */
This text makes it sound like a firm "request" ("if possible").
In the man page posted separately it says:
+.BR RWF_HIPRI " (since Linux 4.6)"
+High priority read/write. Allows block based filesystems to use polling of the
+device, which provides lower latency, but may use additional ressources. (Currently
+only usable on a file descriptor opened using the
+.BR O_DIRECT " flag)."
So now it "allows", which is different again.
The differences may be subtle, but consistency is nice.
Also in that man page fragment:
> provides lower latency, but may use additional ressources
Is this a "latency vs throughput" trade-off, or something more subtle?
It would be nice to make the decision process as obvious as possible for
the developer considering the use of this flag.
(and s/ressources/resources/)
NeilBrown
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