i am asking this doubt with respect to block devices files.... with respect
to cache only
as we know each process have different address spaces so thus this means
that if any general process access block device data ,which already is
present in page cache, will allocate new buffer for the data... or indeed
uses the same buffer which is already there to access the data.Jus i want to
know that new copies of data is created on every access of data ??
On 1/17/07, Peter Staubach <staubach@xxxxxxxxxx> wrote:
gaurav wrote:
> i couldnt understand.."it depends"... depends on what??
> there is no such circumstances... the question is simple...
> for every process whether the kernel allocates new buffer pool for the
> data
> knowing that the processes want to access the same data block....
> or on other hand the processes use only a single copy of data to access
> On 1/17/07, David Howells <dhowells@xxxxxxxxxx> wrote:
>>
>> gaurav <gaurav1207@xxxxxxxxx> wrote:
>>
>> > i wanted to know what exact mechanism takes place at file system
level
>> when
>> > two or more processes try to access the same data from the same
>> disk in
>> > linux 2.6.18 kernel ...
>> > My query is that for every incoming process new buffer is allocated
>> for
>> the
>> > data or the same buffer is used again and again.
>>
>> The answer is: it depends... Can you clarify the circumstances you're
>> asking
>> about? Is this involving FS-Cache?
>>
>> David
>>
Unfortunately, the question is not that simple. It depends upon the
specific implemention for the file system that you are attempting to
access. So, could you explain which file system it is that you are
attempting to get information about? The answer is not system general,
it is file system specific.
Given that, in general, cached data is shared among all processes
accessing the same file.
You posted to the CacheFS list, so one might assume that it is cachefs
that you are asking about. However, this is not clear and thus, David
asked.
Thanx...
ps
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Gaurav....
