Re: Use tmpfs for shm_open()?

Eric W. Biederman (ebiederm+eric@npwt.net)
20 Jun 1998 16:16:00 -0500


>>>>> "RG" == Richard Gooch <Richard.Gooch@atnf.CSIRO.AU> writes:

RG> Eric W. Biederman writes:
>> >>>>> "RG" == Richard Gooch <Richard.Gooch@atnf.CSIRO.AU> writes:
>>
RG> Hi, all. A random thought just popped into my head today: how about
RG> implementing a tmpfs which could then be used as the basis of a simple
RG> userspace (libc) implementation of POSIX shared memory, aka.
RG> shm_open().
What lead me here original is minimizing the number of system calls
needed.
>>
RG> We could kill two birds with one stone, giving a tmpfs to those who
RG> believe it's faster than ext2fs :-), and giving us POSIX SHM too.
>>
>> Plus resource limits could be quotas.
>> I called it shmfs because the emphasis is on being able to do shm_open..
>>
>> Look at http://www.npwt.net/~ebiederm/files
>> and get
>> shmfs-0.1.009.tar.gz
>> and code me that user space implementation please.

RG> Oh. Well done. I must have missed this bit of signal amongst all the
RG> noise. Looks like my idea was sensible (just not original:-).

RG> When do you plan to submit shmfs (somehow I think it's better
RG> described as a memfs or a vmfs, I think shmfs is a bit too specific,
RG> like tmpfs) to Linus?

There is a little more vm work to be done. I have also been working
on a third area that of dirty pages in the page cache, which when it
works should be quite usefull in a lot of ways. I have a working hack
at the minute, and some good code in progress.

If I'm really lucky before 2.2 but otherwise early in 2.3, because of
the dirty pages in the page cache issue.

I could really use someone to write the shm_open user space code.
Working through all of the kernel issues is taking a lot of work, so I
don't think I'll have time for a while.

Eric

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