fcache_seqlimit_file(5)fcache_seqlimit_file(5)NAMEfcache_seqlimit_file - percent of file cache that can be consumed by
sequential accesses, per-file limit
The minimum value allowed is The maximum value allowed is
Specify a positive integer value.
This parameter places a per-file limit on how much memory can be con‐
sumed in the file cache by sequential accesses. It is important to
note the relationship between this tunable and the system-wide limit
tunable, These two tunables, in conjunction, control how much memory in
the file cache can be consumed by sequential accesses.
When sequential accesses to a file has exceeded the per-file limit AND
the system-wide limit, the excess file cache pages are paged out. Note
that both limits have to be reached in order for page stealing to
occur. For example, a file can exceed its limit if the limit has not
been reached. Similarly, no page stealing occurs if none of the files
on the system has exceeded the per-file limit, even if the system-wide
limit has been hit. The page stealing feature is specific to improving
sequential I/O performance for large files.
Limiting the file cache memory consumption helps alleviate memory pres‐
sure in the file cache. It also prevents cache wiping -- a single
thread sequentially accessing a large file can wipe out the existing
contents of the file cache.
Who is Expected to Change This Tunable?
System administrators that run applications which do large sequential
file I/O's. Typically, these files are larger than the size of physi‐
cal memory on the system.
Restrictions on Changing
Changes to this tunable take effect immediately.
When Should the Value of This Tunable Be Raised?
When you wish to allow greater file cache consumption due to sequential
accesses. Setting and to 100 effectively disables the sequential
access page stealing feature.
What Are the Side Effects of Raising the Value?
Setting the tunable too high may yield poor performance for large
sequential I/O's for large files (larger than physical memory size).
and should be tuned appropriately for the anticipated workload.
When Should the Value of This Tunable Be Lowered?
When you wish to limit file cache consumption due to sequential
accesses. Setting and to 0 forces sequential access page stealing to
What Are the Side Effects of Lowering the Value?
Could cause more pageouts to occur in an attempt to limit the file
What Other Tunable Values Should Be Changed at the Same Time?
and should be changed at the same time.
All HP-UX kernel tunable parameters are release specific. This parame‐
ter may be removed or have its meaning changed in future releases of
Installation of optional kernel software, from HP or other vendors, may
cause changes to tunable parameter values. After installation, some
tunable parameters may no longer be at the default or recommended val‐
ues. For information about the effects of installation on tunable val‐
ues, consult the documentation for the kernel software being installed.
For information about optional kernel software that was factory
installed on your system, see at
was developed by HP.
Tunable Kernel Parameters fcache_seqlimit_file(5)