[stgt] [PATCH 1/1] tgtd: Patch to add bsoflags options o tgtd.
Daniel Henrique Debonzi
debonzi at linux.vnet.ibm.com
Tue Jun 29 17:16:55 CEST 2010
FUJITA Tomonori wrote:
> On Thu, 27 May 2010 17:10:43 -0300
> Daniel Henrique Debonzi <debonzi at linux.vnet.ibm.com> wrote:
>> FUJITA Tomonori wrote:
>>> On Tue, 18 May 2010 16:21:00 -0300
>>> Daniel Henrique Debonzi <debonzi at linux.vnet.ibm.com> wrote:
>>>> One idea to solve it and don't make necessary to touch all backing
>>>> stores to avoid this issue is to create a new template like bs_rdrw_sync
>>>> O_SYNC and O_DIRECT flags on open, and don't have the options as this
>>>> patch does. This way I got want I am interested in and don't need to
>>>> involve all the other stuff. What are your thoughts about it?
>>> Or a new option to touch only bs_rdrw.
>>> However, I want to know why you want to use O_SYNC and O_DIRECT.
>>> - what's the advantage of O_SYNC compared with the current approach
>>> (sync_file after write)? notably faster?
>> We would like to be able to control those flags because for our case it
>> has better performance. Some tests done recently showed that we can get
>> good better results when using O_DIRECT than sync_file.
> I see. Thanks for the explanation.
> As we discussed, "--bsoflags" can't be applied to all the bs modes
> equally (e.g. bs_aio can use only O_DIRECT). But I guess that creating
> multiple options such as --bsoflags_rw, --bsoflags_aio, etc is too
> I'll take the approach add only "--bsoflags". --bsoflags="async
> direct" is not consistent with the other options. Let's use "," like
I can't use "," because it is the separator used for the options
--bstype,--bsoflags,etc. If I use it, the second parameter if existente
(like sync,direct) will not be used right. I used ":" once it is also
used for portals (IP:port).
> I don't think that we need "none" or "async". Let's support "sync" and
The async option doesn't exist. It only have sync and direct. The none
option is available only for update. Lets say someone created a target
with sync, and for some reason he doesn't want sync anymore. He can
tgtadm --op update --mode logicalunit --tid 1 --lun 1 --params online=0
tgtadm --op update --mode logicalunit --tid 1 --lun 1 --params\
to clean up the bsoflags.
I put this changes in a separate patch, so you can drop it if you think
it is not necessary.
> Can you please send the updated patch?
I will send the patchs to the list soon.
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