Nx Bypass Cache

[Twyla Plack]

To speed things up and conserve communications bandwidth, browsers attempt to keep local copies of pages, images, and other content you've visited, so that it need not be downloaded again later. Occasionally this caching scheme goes awry (e.g. the browser insists on showing out-of-date content) making it necessary to bypass the cache, thus forcing your browser to re-download a web page's complete, up-to-date content. This is sometimes referred to as a "hard refresh", "cache refresh", or "uncached reload". The rest of your cache is not affected.

When you encounter strange behavior, first try bypassing your cache. In most cases you can use the simple instructions shown to the right, or see the complete browser-specific instructions below. If this is not enough, you can try performing a "purge" of Wikipedia's server cache (see instructions below). If problems persist, report them at Wikipedia:Village pump (technical).

The Wikimedia servers cache a version of articles. When improperly displayed content is contained in a template or other transcluded page, bypassing your own cache might not be enough. You may need to purge the server cache of old page versions.

The server can be instructed to refresh its cache of a page's contents with the action=purge web address parameter. Add this to the end of the address. For example, to purge this page, visit one of the following:

cache(no) vs. bypass_cache(yes)

cache(no)
This indicates that any object previously cached shall be deleted, and that any future acquisition of such object will not be cached. Typically this is used to indicate that specific content should not be cached. Since it is in the cache layer the rule applies to client, pipelined, and refresh requests. This parameter is only used in the layer, specifically the Web Content Layer.

bypass_cache(yes)
This indicates that the cache will not be queried for the content and the webserver's response will also not be cached. Typically this is used to bypass caching for certain source attributes such as source ip, auth username, user-agent, etc. This parameter is only used in the layer, specifically the Web Access Layer.

If bypass_cache(yes) is set, then the cache is not accessed and the value of cache( ) is irrelevant.

bypass_cache() prevents the ProxySG appliance from even checking to see if the object is in cache, meaning any existing cached copy will not be touched and can still be served to other clients which run with bypass_cache(no) policy.

On the other hand, cache(no) prevents the ProxySG appliance from writing any new copy of the object it fetches from the origin server into cache, and in fact will cause it to delete the currently cached copy in that case.

An example of a case use for cache(no) is perhaps as a way to actively flush content which was previously cached out of cache when you decide that caching it is no longer a good idea. That wouldn't happen if you use bypass_cache(yes). If the content can truly never be usefully cached, though, using bypass_cache(yes) will be the most efficient approach since it skips the cache lookup from the very beginning.

Good time of day. I apologise in advance if I am in the wrong section of the forum. I was profiling my Pixel 5 phone (with Snapdragon 765 SOC, whose cpu consists of 1 x Cortex A-76 at 2400 MHz, 1 Cortex x A-76 at 2200 MHz, and 6 x Cortex A-55 at 1800 MHz). I was profiling different applications and I noticed an interesting thing that I find hard to explain. I am doing the profiling with Simpleperf Android tool that collects hardware counters from CPUs PMU. I collected data accesses from 4 levels in memory hierarchy: L1_cache, L2_cache, L3_cache and mem_access.

1. We see that the number of mem accesses is larger than the number of cache accesses (Armv8 architecture documentation states that mem_access hardware event counts accesses to L1 and L2), which means that some accesses did not even attempt to access the cache and went directly to memory. I know that GPUs do that because one can confidently say that data will not be reused and it makes no sense to put that data into cache. Is this what is happening here? I thought that reported mem_accesses were for cpu only.

2. Also If we look at L2 and L3 accesses, we see that there are more L3 accesses than there are L2 accesses, which suggests that some accesses bypassed at least L2 cache and went directly to L3. Does that mean the there is cache bypassing with some accesses bypassing levels of cache hierarchy and going directly to L3? Is there a way to count those accesses?

3. My ultimate goal is to calculate cache misses for some workloads (cache_miss hardware events are not implemented on Pixel 5). I am planning to do that by noting the number of accesses to different levels of memory hierarchy and subtracting appropriate numbers. For example, to calculate L1 misses I am planning to subtract L2 accesses from L1 accesses. This would be a normal method under normal circumstances, but above results got me suspecting that there might be cache bypassing at different levels. If so, is there a way to note how many accesses bypassed each cache level and where they went? So that I can calculate cache misses etc...

I see. Thank you. Do you know if there is a way to detect how many of those were executed from the CPU's PMU? Do they show up as temporal on a system trace? Do you know if it bypasses all caches or only some levels?

I'm copying 10 TB of media files to my new Unraid server using external USB hard drives. I think that the Samsung SSD 1TB cache drive is in the way of the process. The SSD heats up and has stopped the server at least once and therefore I am only copying the files in small batches - also because the cache fills up and stops the process. And now I'm reading that I may be wearing out my brand new SSD. Can I turn off the cache and copy directly to the array? Right now, my SSD has 644 GB used and 355 GB free and I'm wondering if it will ever finish writing to the array - It is going very slowly.

Since my cache is currently showing 866 GB Free and 132 GB used, how can I make sure that my array is updated? The cache is not changing and I'd like to bypass it to finish copying over all of my media files.
Also, I'm still not sure how to bypass the cache. Do I somehow just shut it off while doing the copying? I've been using Krusader and copying to /mnt/user/Media Library.

Thank you. That looks like it will work. But I'm still concerned about the data in the cache that doesn't seem to want to move. I've got 12 folders (Media files) that seem stuck in the cache. Right now there is 57.8 GB used and the Reads and Writes counters are not moving. I select the MOVE button on the bottom and it greys out for a while but does not seem to change anything in the cache.

Follow up question - It is still really slow copying data from my USB drive to the array without the cache. Would it speed up if I temporarily shut off the Parity while copying the data? Right now, it has taken a few hours to copy 200 GB to the array with another 10TB to go.

Are there any potential drawbacks I'm not seeing to using this method to bypass the cache drive for USB transfers? Occasionally I will move large amounts of finished media to the server, and under normal settings this will lead to dumping the data to the mirrored NVMe cache and then later to the HDDs. This seems wasteful, in terms of NVMe i/o, because the cache is serving no real purpose here.

I know I can disable caching for the share, and reenable later, but I'm hesitant to be continually messing with the mover settings like that, especially if they may require an array restart to take effect. So... can I just use the WEBUI filesystem to copy the files directly from my attached SSD drive to the appropriate user0 folder and bypass the cache that way whenever it's necessary? Because that sounds like a far better solution than toggling mover settings every time.

Eh, just found a dumb mistake. The pointer actually worked fine, I just made a bug with bitmasks, so sometimes, shorter numbers passed the mask and longer ones didn't. This was nothing to do with the pointer or cache.

Don't forget that this trick will only work as long as you don't use MMU. If you want your code to be portable to a MMU architecture in the future, you might consider using the alt_remap_uncached() function instead of changing bit 31 on the pointer.

Intel does not verify all solutions, including but not limited to any file transfers that may appear in this community. Accordingly, Intel disclaims all express and implied warranties, including without limitation, the implied warranties of merchantability, fitness for a particular purpose, and non-infringement, as well as any warranty arising from course of performance, course of dealing, or usage in trade.

In order to reduce loading times and save bandwidth when you visit Fandom, your web browser is instructed to save the current view of the page. This is called your "cache". If you visit that page again, your browser will see if there is a newer version of a page available. If there is, the new version is downloaded. If not, it will quickly load much of the page straight from your cache.

Sometimes, however, you might continue to see the cached version of the page even when a newer one is available, for a variety of reasons. This can be frustrating if a change has recently been made to the page.

Bypassing your own cache might not be enough if the updated content is not being properly displayed or is contained in a template or other transcluded page. You may need to purge the server's cache of old versions of the page, by appending the URL with ?action=purge, in order for the new material to be visible.

I changed my gravatar last night, and I can see the new one in Firefox after a Ctrl+F5 refresh, but Chrome seems to be stubbornly hanging on to the old Gravatar. I guess I could manually clear out the cache, but if there is a keyboard command to do it I'd like to know what it is (since it would be helpful for web development too).

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