[SCSI] sr: sr_mutex ,multi-drive performance is bad

[yang jun]

Dear Mr.Axboe,

The latest kernel sr_module still uses single mutex,it will serialise
all sr ioctls. Otto Meta had mentioned this on Jan 1st, 2013 . Some
record tools such as growisofs use SG_IO to write data to disc, so if
there are multiple cdroms being recorded at the same time=A3=ACit will =
be
very slowly.

I saw sd_module before,it had removed BKL and made "openers" atomic_t
in scsi_disk. Shall we do the same thing to sr_module? That is, to
remove sr_mutex and make "use_count" atomic_t in cdrom_device_info.

Yours Sincerely,
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[yang jun]

Dear Mr.Meta

I saw your patch about sr_module, I very curious why the latest kernel
still keep sr_mutex. Can sr_mutex be deleted just like sd_module?

Yours Sincerely

Post by yang jun
Dear Mr.Axboe,
The latest kernel sr_module still uses single mutex,it will serialise
all sr ioctls. Otto Meta had mentioned this on Jan 1st, 2013 . Some
record tools such as growisofs use SG_IO to write data to disc, so if
there are multiple cdroms being recorded at the same time=A3=ACit wil=

l be

Post by yang jun
very slowly.
I saw sd_module before,it had removed BKL and made "openers" atomic_t
in scsi_disk. Shall we do the same thing to sr_module? That is, to
remove sr_mutex and make "use_count" atomic_t in cdrom_device_info.
Yours Sincerely,

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[yang jun]

Dear Mr.Meta

I saw your patch about sr_module, I very curious why the latest kernel
still keep sr_mutex. Can sr_mutex be deleted just like sd_module?

Yours Sincerely

Post by yang jun
Dear Mr.Axboe,
The latest kernel sr_module still uses single mutex,it will serialise
all sr ioctls. Otto Meta had mentioned this on Jan 1st, 2013 . Some
record tools such as growisofs use SG_IO to write data to disc, so if
there are multiple cdroms being recorded at the same time=A3=ACit wil=

l be

Post by yang jun
very slowly.
I saw sd_module before,it had removed BKL and made "openers" atomic_t
in scsi_disk. Shall we do the same thing to sr_module? That is, to
remove sr_mutex and make "use_count" atomic_t in cdrom_device_info.
Yours Sincerely,

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[Jens Axboe]

Post by yang jun
Dear Mr.Axboe,
=20
The latest kernel sr_module still uses single mutex,it will serialise
all sr ioctls. Otto Meta had mentioned this on Jan 1st, 2013 . Some
record tools such as growisofs use SG_IO to write data to disc, so if
there are multiple cdroms being recorded at the same time=A3=ACit wil=

l be

Post by yang jun
very slowly.
=20
I saw sd_module before,it had removed BKL and made "openers" atomic_t
in scsi_disk. Shall we do the same thing to sr_module? That is, to
remove sr_mutex and make "use_count" atomic_t in cdrom_device_info.

The same conversion that happened to sd could apply to sr just as easil=
y.

--=20
Jens Axboe

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[yang jun]

Hi, Jens,

Thanks for your response. When various processes compete for sr_mutex
in .open or .release, the performance will not be worse much, the
main degradation of performance is caused by sr_block_ioctl which
can't release sr_mutex until one io comletes. So, shall we remove
sr_mutex only from sr_block_ioctl but still keep sr_mutex in .open and
=2Erelease? Please advise.

Best regards,
Jun Yang

Post by yang jun
Dear Mr.Axboe,
The latest kernel sr_module still uses single mutex,it will serialis=

e

Post by yang jun
all sr ioctls. Otto Meta had mentioned this on Jan 1st, 2013 . Some
record tools such as growisofs use SG_IO to write data to disc, so i=

f

Post by yang jun
there are multiple cdroms being recorded at the same time=A3=ACit wi=

ll be

Post by yang jun
very slowly.
I saw sd_module before,it had removed BKL and made "openers" atomic_=

t

Post by yang jun
in scsi_disk. Shall we do the same thing to sr_module? That is, to
remove sr_mutex and make "use_count" atomic_t in cdrom_device_info.

The same conversion that happened to sd could apply to sr just as eas=

ily.

--
Jens Axboe

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