VM: Buffer vs. Cache
Hi,
just being curious. Since 2.4.4, I am watching my systems memory
behaviour a bit:-) Just recently I realized the following: in the evening I leave my 128MB system at about 20 MB, 2 MB Buffered and 100 MB Cached (plus som 40 MB unneccesary swap :-)). When I come back in the morning, Used is still at 20 MB (a bit down maybe) but Buffered is 50 MB and Cached is 55 MB. For a few minutes the system is definitely more sluggish than in the evening. Something I can excuse before my first cup of coffe anyway...
So, what actually is the difference between Buffered and Cached.
Apparently quite a lot of the pages that are Cached in the evening are Buffered 9 houres later.
Thanks
Martin
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Quoted 9 lines
just being curious. Since 2.4.4, I am watching my systems memory behaviour a bit:-) Just recently I realized the following: in the evening I leave my 128MB system at about 20 MB, 2 MB Buffered and 100 MB Cached (plus som 40 MB unneccesary swap :-)). When I come back in the morning, Used is still at 20 MB (a bit down maybe) but Buffered is 50 MB and Cached is 55 MB. For a few minutes the system is definitely more sluggish than in the evening. Something I can excuse before my first cup of coffe anyway...
Quoted 3 lines
So, what actually is the difference between Buffered and Cached. Apparently quite a lot of the pages that are Cached in the evening are Buffered 9 houres later.
Think about what happens in the meantime. Most distros install maintenance scripts which run late at night (usually at midnight and/or 4am), which perform heavy disk activity as they update databases and scan for file-permissions security holes. Heavy disk activity usually means an increase in buffer utilisation. Since most files are only "touched" once, the cache is shrunk as it aren't being used very much.
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from: Jonathan "Chromatix" Morton mail: [email protected] (not for attachments)
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Quoted 6 lines · Jonathan Morton
Quoted 5 lines
So, what actually is the difference between Buffered and Cached. Apparently quite a lot of the pages that are Cached in the evening are Buffered 9 houres later.
Quoted 7 lines
Think about what happens in the meantime. Most distros install maintenance scripts which run late at night (usually at midnight and/or 4am), which perform heavy disk activity as they update databases and scan for file-permissions security holes. Heavy disk activity usually means an increase in buffer utilisation. Since most files are only "touched" once, the cache is shrunk as it aren't being used very much.
thanks to all who set me straight. Should have thought of the nightly
stuff myself.
Martin
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------------------------------------------------------------------ Martin Knoblauch | email: [email protected] TeraPort GmbH | Phone: +49-89-510857-309 C+ITS | Fax: +49-89-510857-111 http://www.teraport.de | Mobile: +49-170-4904759