Date: Mon, 23 Feb 2009 11:58:09 -0800 From: Garrett Cooper <yanefbsd@gmail.com> To: Christian Peron <csjp@FreeBSD.org> Cc: Kirk Strauser <kirk@strauser.com>, freebsd-hackers@freebsd.org, "Brian A. Seklecki" <lavalamp@spiritual-machines.org>, wmoran@potentialtech.com Subject: Re: shmmax tops out at 2G? Message-ID: <78AACD88-3F94-4B39-9122-9C4199DFFDBA@gmail.com> In-Reply-To: <20090223190828.GA34866@jnz.sqrt.ca> References: <1235404207.31655.2085.camel@soundwave.ws.pitbpa0.priv.collaborativefusion.com> <20090223190828.GA34866@jnz.sqrt.ca>
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On Feb 23, 2009, at 11:08 AM, Christian Peron wrote:
> This issue has come up a number of times. I was looking into fixing
> this but I
> just have not had the time. The basic issue is our shmid_ds
> structure:
>
> struct shmid_ds {
> struct ipc_perm shm_perm; /* operation permission
> structure */
> int shm_segsz; /* size of segment in bytes */
> pid_t shm_lpid; /* process ID of last shared
> memory op */
> pid_t shm_cpid; /* process ID of creator */
> short shm_nattch; /* number of current attaches */
> time_t shm_atime; /* time of last shmat() */
> time_t shm_dtime; /* time of last shmdt() */
> time_t shm_ctime; /* time of last change by
> shmctl() */
> void *shm_internal; /* sysv stupidity */
> };
>
>
> Basically the shm_segsz member needs to be switched from 32 bits
> (int) to
> 64 bits. The problem is that this breaks the ABI and older versions
> of
> postgresql will not work. The solution is to add additional syscalls.
>
> However, everytime this issue comes up, the question on whether we
> should
> fix struct ipc_perm at the same time is asked. The answer imho is
> that
> we should, however this is more complex since semaphores, messaages
> and
> shared memory segments all use it.
>
> The fixes are straight forward, however making sure we maintain
> reverse
> compatability is where things become complicated, especially since
> there
> are multiple layers of reverse compat we need to look after.
>
>
> On Mon, Feb 23, 2009 at 10:50:07AM -0500, Brian A. Seklecki wrote:
>>> On Wed, 2006-Dec-13 10:50:21 -0500, Bill Moran wrote:
>>>> In response to Bill Moran <wmoran at collaborativefusion.com>:
>>>>> sysctl kern.ipc.shmmax=2200000000
>>>>> kern.ipc.shmmax: 2100000000 -> -2094967296
>>
>> Someone was nice enough to file a PR related to this:
>>
>> http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/130274
>>
>> We'd be happy to sponsor development in -current to address this
>> limitation. ~BAS
Why isn't the field an unsigned int / size_t? I don't see much value
in having the size be signed...
-Garrett
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