user/sven/linux.git/drivers/misc/vmw_balloon.c, branch v4.20

vmw_balloon: add reset stat

2018-09-25T18:11:43Z

It is useful to expose how many times the balloon resets. If it happens more than very rarely - this is an indication for a problem. Reviewed-by: Xavier Deguillard Signed-off-by: Nadav Amit Signed-off-by: Greg Kroah-Hartman

vmw_balloon: general style cleanup

2018-09-25T18:11:43Z

Change all the remaining return values to int to avoid mistakes. Reduce indentation when possible. Reviewed-by: Xavier Deguillard Signed-off-by: Nadav Amit Signed-off-by: Greg Kroah-Hartman

vmw_balloon: rework the inflate and deflate loops

2018-09-25T18:11:42Z

In preparation for supporting compaction and OOM notification, this patch reworks the inflate/deflate loops. The main idea is to separate the allocation, communication with the hypervisor, and the handling of errors from each other. Doing will allow us to perform concurrent inflation and deflation, excluding the actual communication with the hypervisor. To do so, we need to get rid of the remaining global state that is kept in the balloon struct, specifically the refuse_list. When the VM communicates with the hypervisor, it does not free or put back pages to the balloon list and instead only moves the pages whose status indicated failure into a refuse_list on the stack. Once the operation completes, the inflation or deflation functions handle the list appropriately. As we do that, we can consolidate the communication with the hypervisor for both the lock and unlock operations into a single function. We also reuse the deflation function for popping the balloon. As a preparation for preventing races, we hold a spinlock when the communication actually takes place, and use atomic operations for updating the balloon size. The balloon page list is still racy and will be handled in the next patch. Reviewed-by: Xavier Deguillard Signed-off-by: Nadav Amit Signed-off-by: Greg Kroah-Hartman

vmw_balloon: stats rework

2018-09-25T18:11:42Z

To allow the balloon statistics to be updated concurrently, we change the statistics to be held per core and aggregate it when needed. To avoid the memory overhead of keeping the statistics per core, and since it is likely not used by most users, we start updating the statistics only after the first use. A read-write semaphore is used to protect the statistics initialization and avoid races. This semaphore is (and will) be used to protect configuration changes during reset. While we are at it, address some other issues: change the statistics update to inline functions instead of define; use ulong for saving the statistics; and clean the statistics printouts. Note that this patch changes the format of the outputs. If there are any automatic tools that use the statistics, they might fail. Reviewed-by: Xavier Deguillard Signed-off-by: Nadav Amit Signed-off-by: Greg Kroah-Hartman

vmw_balloon: simplify vmballoon_send_get_target()

2018-09-25T18:11:42Z

As we want to leave as little as possible on the global balloon structure, to avoid possible future races, we want to get rid sysinfo. We can actually get the total_ram directly, and simplify the logic of vmballoon_send_get_target() a little. While we are doing that, let's return int and avoid mistakes due to bool/int conversions. Reviewed-by: Xavier Deguillard Signed-off-by: Nadav Amit Signed-off-by: Greg Kroah-Hartman

vmw_balloon: refactor change size from vmballoon_work

2018-09-25T18:11:42Z

The required change in the balloon size is currently computed in vmballoon_work(), vmballoon_inflate() and vmballoon_deflate(). Refactor it to simplify the next patches. Reviewed-by: Xavier Deguillard Signed-off-by: Nadav Amit Signed-off-by: Greg Kroah-Hartman

vmw_balloon: rename VMW_BALLOON_2M_SHIFT to VMW_BALLOON_2M_ORDER

2018-09-25T18:11:42Z

The name of the macro'd VMW_BALLOON_2M_SHIFT is misleading. The value reflects 2M huge-page order. Unfortunately, we cannot use HPAGE_PMD_ORDER, since it is not defined when transparent huge-pages are off, so we need to define our own one. Rename it to VMW_BALLOON_2M_ORDER. No functional change. Signed-off-by: Nadav Amit Signed-off-by: Greg Kroah-Hartman

vmw_balloon: treat all refused pages equally

2018-09-25T18:11:42Z

Currently, when the hypervisor rejects a page during lock operation, the VM treats pages differently according to the error-code: in certain cases the page is immediately freed, and in others it is put on a rejection list and only freed later. The behavior does not make too much sense. If the page is freed immediately it is very likely to be used again in the next batch of allocations, and be rejected again. In addition, for support of compaction and OOM notifiers, we wish to separate the logic that communicates with the hypervisor (as well as analyzes the status of each page) from the logic that allocates or free pages. Treat all errors the same way, queuing the pages on the refuse list. Move to the next allocation size (4k) when too many pages are refused. Free the refused pages when moving to the next size to avoid situations in which too much memory is waiting to be freed on the refused list. Reviewed-by: Xavier Deguillard Signed-off-by: Nadav Amit Signed-off-by: Greg Kroah-Hartman

vmw_balloon: change batch/single lock abstractions

2018-09-25T18:11:42Z

The current abstractions for batch vs single operations seem suboptimal and complicate the implementation of additional features (OOM, compaction). The immediate problem of the current abstractions is that they cause differences in how operations are handled when batching is on or off. For example, the refused_alloc counter is not updated when batching is on. These discrepancies are caused by code redundancies. Instead, this patch presents three type of operations, according to whether batching is on or off: (1) add page, (2) communication with the hypervisor and (3) retrieving the status of a page. To avoid the overhead of virtual functions, and since we do not expect additional interfaces for communication with the hypervisor, we use static keys instead of virtual functions. Finally, while we are at it, change vmballoon_init_batching() to return int instead of bool, to be consistent in the return type and avoid potential coding errors. Reviewed-by: Xavier Deguillard Signed-off-by: Nadav Amit Signed-off-by: Greg Kroah-Hartman

vmw_balloon: remove sleeping allocations

2018-09-25T18:11:42Z

Splitting the allocations between sleeping and non-sleeping made some sort of sense as long as rate-limiting was enabled. Now that it is removed, we need to decide - either we want sleeping allocations or not. Since no other Linux balloon driver (hv, Xen, virtio) uses sleeping allocations, use the same approach. We do distinguish, however, between 2MB allocations and 4kB allocations and prevent reclamation on 2MB. In both cases, we avoid using emergency low-memory pools, as it may cause undesired effects. Reviewed-by: Xavier Deguillard Signed-off-by: Nadav Amit Signed-off-by: Greg Kroah-Hartman