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Full Discussion: CIO/DIO and JFS2 read ahead
Operating Systems AIX CIO/DIO and JFS2 read ahead Post 302258257 by zaxxon on Friday 14th of November 2008 06:45:13 AM
Old 11-14-2008
As Shockneck said, CIO/DIO is said to be better for random reads/write afaik.

You could check with vmstat -v if there are still any blocked buffers counting up and tune them with the appropriate ioo parameters.
Also you can check about aio, if there is any usage of it or something close to it's limits with "iostat -A" and also the shift+a option in nmon, to see how many aioservers are being used currently.

Edit:
Ah I see we had a foregoing discussion already here
https://www.unix.com/unix-advanced-ex...evice-cio.html

Are you sure you need cio? You hadn't shown the "vmstat -v" back then still.

There is also the possibility to change attributes for FC adapter (like lg_term_dma, max_xfer_size and num_cmd_elems) and disks (like queue_depth or max_coalesce) with chdev and reading them out with lsattr. But before doing that, I would start to sort things out with AIO if appropriate and vmstat -v/iostat.

Last edited by zaxxon; 11-14-2008 at 08:23 AM.. Reason: Added something, and something more
 

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VM_PAGE_GRAB(9) 					   BSD Kernel Developer's Manual					   VM_PAGE_GRAB(9)

NAME
vm_page_grab -- returns a page from an object SYNOPSIS
#include <sys/param.h> #include <vm/vm.h> #include <vm/vm_page.h> vm_page_t vm_page_grab(vm_object_t object, vm_pindex_t pindex, int allocflags); DESCRIPTION
The vm_page_grab() function returns the page at pindex from the given object. If the page exists and is busy, vm_page_grab() will sleep while waiting for it. If the page does not exist, it is allocated. The function sleeps until the allocation request can be satisfied. The function requires the object to be locked on entry, and returns with the object locked. If the vm_page_grab() function sleeps for any reason, the object lock is temporary dropped. The vm_page_grab() supports all of the flags supported by vm_page_alloc(9). In addition, vm_page_grab() supports the following flags: VM_ALLOC_IGN_SBUSY When waiting for the busy state of the existing page to drain, only test for exclusive busy; ignore the shared busy counter. RETURN VALUES
The vm_page_grab() always returns the page. SEE ALSO
vm_page_alloc(9) AUTHORS
This manual page was written by Chad David <davidc@acns.ab.ca>. BSD
August 23, 2013 BSD
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